Systems and methods for joint replacement

ABSTRACT

Systems and methods for joint replacement are provided. The systems and methods include a surgical orientation device and at least one orthopedic fixture. The surgical orientation device and orthopedic fixtures can be used to locate the orientation of an axis in the body, to adjust an orientation of a cutting plane or planes along a bony surface, to distract a joint, or to otherwise assist in an orthopedic procedure or procedures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/102,754, filed Oct. 3, 2008, U.S.Provisional Patent Application No. 61/135,863, filed Jul. 24, 2008, U.S.Provisional Patent Application No. 61/102,767, filed Oct. 3, 2008, U.S.Provisional Patent Application No. 61/155,093, filed Feb. 24, 2009, U.S.Provisional Patent Application No. 61/104,644, filed Oct. 10, 2008, U.S.Provisional Patent Application No. 61/153,268, filed Feb. 17, 2009, U.S.Provisional Patent Application No. 61/153,257, filed Feb. 17, 2009, U.S.Provisional Patent Application No. 61/153,255, filed Feb. 17, 2009, U.S.Provisional Patent Application No. 61/173,158, filed Apr. 27, 2009, U.S.Provisional Patent Application No. 61/187,632, filed Jun. 16, 2009, andU.S. Provisional Patent Application No. 61/173,159, filed Apr. 27, 2009,each of which is incorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTIONS

1. Field of the Inventions

The present application is directed to systems and methods for jointreplacement, in particular to systems and methods for knee jointreplacement which utilize a surgical orientation device or devices.

2. Description of the Related Art

Joint replacement procedures, including knee joint replacementprocedures, are commonly used to replace a patient's joint with aprosthetic joint component or components. Such procedures often use asystem or systems of surgical tools and devices, including but notlimited to cutting guides (e.g. cutting blocks) and surgical guides, tomake surgical cuts along a portion or portions of the patient's bone.

Current systems and methods often use expensive, complex, bulky, and/ormassive computer navigation systems which require a computer orcomputers, as well as three dimensional imaging, to track a spatiallocation and/or movement of a surgical instrument or landmark in thehuman body. These systems are used generally to assist a user todetermine where in space a tool or landmark is located, and oftenrequire extensive training, cost, and room.

Where such complex and costly system are not used, simple methods areused, such “eyeballing” the alignment of rods with anatomical features,such as leg bones. These simple methods are not sufficiently accurate toreliably align and place implant components and the bones to which suchcomponents are attached.

SUMMARY OF THE INVENTIONS

Accordingly, there is a lack of devices, systems and methods that can beused to accurately position components of prosthetic joints withoutoverly complicating the procedures, crowding the medical personnel,and/or burdening the physician of health-care facility with the greatcost of complex navigation systems.

In accordance with at least one embodiment, a surgical orientationdevice for use in a total knee arthroplasty procedure having anassociated three-dimensional coordinate reference system can comprise aportable housing configured to connect to a knee bone by way of one ormore orthopedic fixtures, a sensor located within the housing, thesensor configured to monitor the orientation of the housing in thethree-dimensional coordinate reference system, the sensor furtherconfigured to generate orientation data corresponding to the monitoredorientation of the surgical orientation device, and wherein the sensorcomprises a multi-axis accelerometer. The surgical orientation devicecan further comprise a display module configured to display one or moreangle measurements corresponding to an offset from a flexion-extensionangle or a varus-valgus angle of a mechanical axis of the knee joint,and wherein the sensor can be oriented relative to the housing at anacute angle to maximize the sensitivity of the sensor when coupled to atibia or a femur.

In accordance with another embodiment, an orthopedic orientation systemfor use in a joint procedure can comprise an orthopedic fixture adaptedto be coupled with a knee bone and to be adjustable in multiple degreesof freedom, and a surgical orientation device having an associatedthree-dimensional coordinate reference system. The device can comprise aportable housing configured to connect to a knee bone by way of theorthopedic fixtures, and a sensor located within the housing, the sensorconfigured to monitor the orientation of the housing in thethree-dimensional coordinate reference system, the sensor furtherconfigured to generate orientation data corresponding to the monitoredorientation of the surgical orientation device. The surgical orientationdevice can further comprise an output device configured to inform a userof the orientation of the device relative to a reference planecorresponding to a mechanical axis of the joint, and wherein the sensorcan be configured for optimum sensitivity in the range of motion of theorthopedic fixture.

In accordance with at least one embodiment, an orthopedic system fororienting a cutting plane during a joint replacement procedure cancomprise a base member attachable to an anterior face of a tibia, atleast one adjustment device connected to and moveable relative to thebase member, and at least one probe for referencing a plurality ofanatomical landmarks, the anatomical landmarks referencing a mechanicalaxis of the leg. The at least one adjustment device can be moveable inat least one degree of freedom so as to orient a cutting guide relativeto a proximal feature of the tibia, such that the cutting guide isoriented at a selected angle relative to the mechanical axis.

In accordance with at least one embodiment, an interactive userinterface for aiding a user in performing an orthopedic procedure can beprovided, wherein the user interface is displayed on a displayassociated with a surgical orientation device configured to monitor theorientation of the surgical orientation device in a three-dimensionalcoordinate reference system and wherein the user interface is configuredto perform acts comprising showing the user steps to be performed in theidentified orthopedic procedure and guiding the user in performance ofthe steps. Guiding the user can comprise displaying one or moreinstructive images related to a first step to be performed in theidentified orthopedic procedure, prompting the user to press a userinput after performing the first step of the identified orthopedicprocedure, receiving a confirmation from the user that the first step ofthe identified procedure has been performed, and displaying one or moreinstructive images related to the second step to be performed in theidentified orthopedic procedure.

In accordance with another embodiment, a monitoring system can beprovided for monitoring an orientation of a surgical orientation devicehaving an associated three-dimensional coordinate reference systemduring an orthopedic procedure, the orientation system comprising adisplay having a window and an on-screen graphic, displayed in thewindow and representing one or more orientation measurementscorresponding to an orientation of the surgical orientation device aboutone or more axes of the three-dimensional coordinate reference system,the one or more orientation measurements generated by a processor.

In accordance with at least one embodiment, a method for preparing aproximal portion of a tibia for receiving a knee implant can comprisecoupling an orthopedic fixture with a proximal feature of the patient'sleg, connecting a portable surgical orientation device to an adjustmentdevice that is connected to the orthopedic fixture and moveable relativeto the leg, moving the adjustment device to move the portable surgicalorientation device in response to a prompt from the portable surgicalorientation device to orient the orthopedic fixture relative to amechanical axis of the leg.

In accordance with another embodiment, a method for performing totalknee arthroplasty on a knee joint of a patient can comprise preparing aproximal portion of a tibia for receiving a knee implant, includingcoupling an orthopedic fixture with a proximal portion of the patient'stibia, connecting a portable surgical orientation device to a moveableportion of the orthopedic fixture, moving the moveable portion of theorthopedic fixture to move the portable surgical orientation device inresponse to a prompt from the portable surgical orientation device toorient a cutting guide at an intended orientation relative to amechanical axis of the leg, and resecting the proximal tibia along thecutting guide to define a tibial plateau. The method can furthercomprise preparing a distal portion of a femur for receiving a kneeimplant, including coupling an orthopedic fixture and the portablesurgical orientation device with an anterior surface of a distal portionof the femur, moving at least one of the femur and the tibia in responseto a prompt from the portable surgical orientation device to align thefemur with the mechanical axis of the leg, securing a cutting guide withan anterior feature of the femur such that the guide is substantiallyperpendicular to the mechanical axis, and resecting the distal femur.

In accordance with another embodiment, a method of performing anorthopedic procedure can comprise coupling an orthopedic fixture and theportable surgical orientation device with a distal portion of a limbthat comprises a portion of a ball-and-socket joint, the portablesurgical orientation device including a housing enclosing a sensor and amicroprocessor. The method can further comprise activating the sensorwithin the portable surgical orientation device, such that the sensoroutputs a signal indicative of orientation, collecting positionalinformation of the portable surgical orientation device; and determiningthe location of the mechanical axis of the limb based on the positionalinformation collected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a representation of a human leg, identifying the femoralhead, knee joint, femur, tibia, and ankle;

FIG. 2A is a perspective view of a tibial preparation system accordingto one embodiment that can be used in connection with preparation of anaspect of a knee joint during a knee joint replacement procedure;

FIG. 2B is a perspective view of another tibial preparation systemaccording to one embodiment that can be used in connection withpreparation of an aspect of a knee joint during a knee joint replacementprocedure;

FIG. 3A is a perspective view of a first arrangement of another tibialpreparation system according to one embodiment that can be used inconnection with preparation of an aspect of a knee joint during a kneejoint replacement procedure;

FIG. 3B is a perspective view of a second arrangement of the tibialpreparation system of FIG. 3A;

FIG. 4A is a perspective view of a first arrangement of another tibialpreparation system according to one embodiment that can be used inconnection with preparation of an aspect of a knee joint during a kneejoint replacement procedure;

FIG. 4B is a perspective view of a second arrangement of the tibialpreparation system of FIG. 4A;

FIG. 5 is a perspective view of femoral preparation system according toone embodiment that can be used in connection with preparation of anaspect of a knee joint during a knee joint replacement procedure;

FIG. 6 is a perspective view of a femoral preparation and kneedistraction system according to one embodiment that can be used inconnection with preparation of an aspect of a knee joint during a kneejoint replacement procedure;

FIG. 7 is a perspective view of a surgical orientation device accordingto one embodiment that can be used for orienting a resection plane orplanes;

FIG. 8 is a back view of the surgical orientation device of FIG. 7;

FIG. 9 is a perspective view of the surgical orientation device of FIG.7;

FIG. 10A is a top view of the surgical orientation device of FIG. 7;

FIG. 10B is a bottom view of the surgical orientation device of FIG. 7;

FIG. 11 is a block diagram of an electrical system of the surgicalorientation device of FIG. 7;

FIGS. 12A-12C illustrate operation of accelerometers according toembodiments that can be used as sensors in the electrical system of FIG.11;

FIG. 12D is a perspective view of interior components of the surgicalorientation device of FIG. 7;

FIG. 12E is a flow chart of an embodiment of an orientation measurementprocess performed by the surgical orientation device of FIG. 7;

FIG. 12F is a side view of a left leg of a patient illustrating anorientation reference frame;

FIG. 13 is a perspective view of a surgical orientation device accordingto another embodiment;

FIG. 14 is a perspective view of a coupling device according to oneembodiment that can be used to connect the surgical orientation deviceof FIG. 7 to other components;

FIG. 15 is a perspective view an outer housing of the coupling device ofFIG. 14;

FIG. 16 is a perspective view of interior components of the couplingdevice of FIG. 14;

FIG. 17 is a plan view of the coupling device of FIG. 14;

FIG. 17A is an exploded view a coupling device according to anotherembodiment;

FIG. 18 is a perspective view of an orthopedic fixture according to oneembodiment which can be used as a universal jig;

FIG. 19 is an exploded view of the orthopedic fixture of FIG. 18;

FIG. 20 is a perspective view of a set of target probes according to oneembodiment which can be used in conjunction with the orthopedic fixtureof FIG. 18;

FIG. 21A is a perspective view of the tibial preparation system of FIG.2A attached to the tibia;

FIG. 21B is a perspective view of a tibial preparation system, asmodified from the tibial preparation system of FIG. 2A, emitting laserlight onto a target probe;

FIG. 22A is a perspective view of the tibial preparation system of FIG.2B;

FIG. 22B is a side view of the tibial preparation system of FIG. 2B;

FIG. 22C is a perspective view of the tibial preparation system of FIG.2B, without a surgical orientation device attached;

FIG. 23A is a perspective view of a tibial preparation system, asmodified from the tibial preparation system of FIG. 2B, showingmeasuring devices;

FIG. 23B is a perspective view of the tibial preparation system of FIG.23A being used to reference an anatomical landmark;

FIG. 24 is a perspective view of a landmark acquisition assemblyaccording to one embodiment that can be used in the tibial preparationsystem of FIG. 3A;

FIGS. 25A-B are perspective views of a primary and secondary rod of thelandmark acquisition assembly of FIG. 24;

FIG. 26 is a front view of a connecting element of the landmarkacquisition assembly of FIG. 24;

FIG. 27 is a perspective view of the second arrangement of the tibialpreparation system of FIG. 3B, showing an extramedullary alignment guideaccording to one embodiment that can be used along the anterior side ofthe tibia;

FIGS. 28 and 29 are perspective views of the first arrangement of thetibial preparation system of FIG. 3A during a knee joint replacementprocedure;

FIGS. 30-36B are perspective views of the second arrangement of thetibial preparation system of FIG. 3B during a knee joint replacementprocedure;

FIG. 37 is a perspective view of a cutting block and a cutting toolbeing used to resect a portion of the proximal tibia;

FIG. 38 is a perspective view of the tibial preparation system of FIG.4B during a knee joint replacement procedure;

FIG. 39 is a perspective view of a the second arrangement of the tibialpreparation system of FIG. 4B

FIG. 40 is a perspective view of an orthopedic fixture according to oneembodiment which can be used in the femoral preparation system of FIG.5;

FIG. 41 is an exploded view of the orthopedic fixture of FIG. 40;

FIG. 42 is a perspective view of the femoral preparation system of FIG.5 during a stage of a knee joint replacement procedure;

FIG. 43 is a perspective view of the femoral preparation system of FIG.5 during another stage of a knee joint replacement procedure;

FIG. 44 is a perspective view of a distraction device according to oneembodiment which can be used in the femoral preparation system of FIG.6;

FIG. 45 is a side view of the distraction device of FIG. 44;

FIG. 46 is a top view of the distraction device of FIG. 44;

FIG. 47 is a partial perspective view of a portion of the distractiondevice of FIG. 44;

FIG. 48 is a perspective view of a portion of the distraction device ofFIG. 44;

FIGS. 49A-B are anterior views of the femoral preparation system of FIG.5 being used to distract a knee joint with visual guidance using avisual indicator, such as a laser;

FIG. 50A is an anterior view of the femoral preparation system of FIG. 5after the knee has been distracted;

FIG. 50B is an anterior view of the femoral preparation system of FIG. 5after the knee has been distracted;

FIG. 51A is a perspective view of a first pin being inserted into anopening in the femoral preparation system of FIG. 5;

FIG. 51B is a perspective view of a second pin being inserted into anopening in the femoral preparation system of FIG. 5;

FIG. 52 is a perspective view of a cutting block and a cutting toolbeing used to resect a portion of the distal femur;

FIG. 53 is an anterior view of the femoral preparation system of FIG. 5being used to distract a knee joint with visual guidance using a visualindicator, such as a laser;

FIG. 54 is an anterior view of the femoral preparation system of FIG. 5being used to distract a knee joint with visual guidance using a visualindicator, such as a laser;

FIG. 55 is an anterior view of the femoral preparation system of FIG. 5being used to distract a knee joint with visual guidance using a visualindicator, such as a laser;

FIG. 56 is a perspective view of the femoral preparation system of FIG.5 after the knee has been distracted;

FIG. 57 is a perspective view of a cutting block which can be used toresect the distal femur;

FIGS. 58A-61K show screen displays generated by one embodiment of theinteractive user interface of the surgical orientation device of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although certain preferred embodiments and examples are disclosed below,it will be understood by those skilled in the art that the inventivesubject matter extends beyond the specifically disclosed embodiments toother alternative embodiments and/or uses of the invention, and toobvious modifications and equivalents thereof. Thus it is intended thatthe scope of the inventions herein disclosed should not be limited bythe particular disclosed embodiments described below. Thus, for example,in any method or process disclosed herein, the acts or operations makingup the method/process may be performed in any suitable sequence, and arenot necessarily limited to any particular disclosed sequence. Forpurposes of contrasting various embodiments with the prior art, certainaspects and advantages of these embodiments are described whereappropriate herein. Of course, it is to be understood that notnecessarily all such aspects or advantages may be achieved in accordancewith any particular embodiment. Thus, for example, it should berecognized that the various embodiments may be carried out in a mannerthat achieves or optimizes one advantage or group of advantages astaught herein without necessarily achieving other aspects or advantagesas may be taught or suggested herein.

In addition, in the following description of the invention, a “module”includes, but is not limited to, software or hardware components whichperform certain tasks. Thus, a module may include object-orientedsoftware components, class components, procedures, subroutines, datastructures, segments of program code, drivers, firmware, microcode,circuitry, data, tables, arrays, etc. Those with ordinary skill in theart will also recognize that a module can be implemented using a widevariety of different software and hardware techniques.

The following sections describe in detail systems and methods for atotal knee joint replacement procedure. The knee joint often requiresreplacement in the form of prosthetic components due to strain, stress,wear, deformation, misalignment, and/or other conditions in the joint.Prosthetic knee joint components are designed to replace a distalportion or portions of a femur and/or a proximal portion or portions ofa tibia.

FIG. 1 illustrates a femur F and tibia T, with the distal portion of thefemur F and proximal portion of the tibia T forming the knee joint. Toprovide the reader with the proper orientation of the instruments and toassist in more fully understanding the construction of the instruments,a small chart is included on many of the figures. The charts indicatethe general directions—anterior, posterior, medial, and lateral, as wellas proximal and distal. These terms relate to the orientation of theknee bones, such as the femur and tibia and will be used in thedescriptions of the various instruments consistent with their knownmedical usage. Additionally, the terms varus/valgus andposterior/anterior are used herein to describe directional movement.Varus/valgus is a broad term as used herein, and includes, withoutlimitation, rotational movement in a medial and/or lateral directionrelative to the knee joint shown in FIG. 1. Posterior/anterior is abroad term as used herein, and includes, without limitation, rotationalmovement in a posterior and/or anterior direction (e.g. in aflexion/extension direction) relative to the knee joint shown in FIG. 1.

Prior to replacing the knee joint with prosthetic components, surgicalcuts commonly called resections are generally made with a cutting toolor tools along a portion or portions of both the proximal tibia anddistal femur. These cuts are made to prepare the tibia and femur for theprosthetic components. After these cuts are made, the prostheticcomponents can be attached and/or secured to the tibia and femur.

The desired orientation and/or position of these cuts, and of theprosthetic components, can be determined pre-operatively and based, forexample, on a mechanical axis running through an individual patient'sleg. Once the desired locations of these cuts are determinedpre-operatively, the surgeon can use the systems and methods describedherein to make these cuts accurately. While the systems and methods aredescribed in the context of a knee joint replacement procedure, thesystems and/or their components and methods can similarly be used inother types of medical procedures, including but not limited to shoulderand hip replacement procedures.

I. Overview of Systems and Methods

FIGS. 2-6 show various systems which can be used in orthopedicprocedures, such as joint replacement procedures. Such systems caninclude a tibial preparation system 10, a femoral preparation system510, and a knee distraction and femoral preparation system 610. Asdescribed below, each of these systems can be embodied in a number ofvariations with different advantages.

II. Tibial Preparation Systems and Methods

A number of different tibial preparation systems are discussed below.These systems are useful for modifying the natural tibia to enable it tohave a prosthetic component securely mounted upon it.

A. Tibial Preparation System with Target Probes

With reference to FIG. 2 a, a tibial preparation system 10 can comprisea surgical orientation device 12, or other measuring device, which canbe used to measure and record the location of anatomical landmarks ofuse in a total knee procedure, such as the location of the mechanicalaxis of the leg. The mechanical axis of the leg, as defined herein,generally refers to an axial line extending from the center of rotationof a proximal head of a femur (e.g. the center of the femoral head)through the center of the knee, to a center, or mid-point, of the ankle(see, for example, FIG. 1). Generally, an ideal mechanical axis in apatient allows load to pass from the center of the hip, through thecenter of the knee, and to the center of the ankle. The tibialpreparation system 10 also can include a coupling device 14, a universaljig 16, and target probes 18 a, 18 b.

As used herein, the term “universal jig” is a broad term and includes,without limitation, orthopedic fixtures that are adapted to be connectedto or coupled with, directly or indirectly, an anatomical structure,such as a bone, a limb, a portion of a joint, and to be moveable in oneor more degrees of freedom, and in some cases is multiple degrees offreedom. As discussed further below, the universal jig 16 can be oneform of an orthopedic fixture that can be used to couple the surgicalorientation device 12 with a bone adjacent to a knee joint. In certaintechniques discussed below the surgical orientation device 12 is usedwith a plurality of orthopedic fixtures. The coupling device 14advantageously enables the surgical orientation device 12 to be quicklycoupled and decoupled with a variety of orthopedic fixtures during theprocedure. This enables the surgical orientation device 12 to be used ina modular fashion, with a variety of orthopedic fixtures at one or morestages of a procedure.

1. Surgical Orientation Device for Verifying Alignment of OrthopedicFixtures

A surgical orientation device can be provided which can be used forverifying an alignment of an orthopedic fixture or fixtures, or acutting plane or planes, during an orthopedic procedure. Surgicalorientation device is a broad term as used herein, and includes, withoutlimitation, devices which can be used alone or in conjunction with anorthopedic fixture or fixtures to orient a cutting plane during anorthopedic procedure or to otherwise identify or track a relativeposition of one or more surgical devices or anatomical structures, andcan encompass any of the embodiments shown in the drawings and asdescribed herein. For example, FIG. 7 shows an embodiment of a surgicalorientation device 12. The surgical orientation device 12 can comprise acompact, generally hand-held and/or portable device for use in orientinga cutting guide or other surgical tool in a joint replacement procedure.The surgical orientation device 12 can be used to locate a portion ofthe mechanical axis that extends through the lower tibia or a portionthereof. Also, the surgical orientation device 12 can be used to locatea portion of the mechanical axis that extends through the femur or aportion thereof. In certain techniques discussed below, the surgicalorientation device 12 is used to locate one, two, or more planesintersecting the mechanical axis. The surgical orientation device 12, asdescribed herein, can be used alone or in conjunction with otherdevices, components, and/or systems.

In a preferred arrangement, the surgical orientation device 12 cancomprise a generally rectangular-shaped, box-like structure having anouter housing 20. The outer housing 20 can be portable. The outerhousing 20 can be comprised, at least in part, of plastic including butnot limited to ABS, polycarbonate, or other suitable material. Thesurgical orientation device 12 can be configured for hand-held use.

With continued reference to FIG. 7, a front side 22, or a portion of thefront side 22, of the surgical orientation device 12 can comprise adisplay 24. The display 24 can be a separate component from the outerhousing 20 or can be integrated on or within the outer housing 20. Thedisplay 24 can comprise an output device. For example, the display 24can comprise a liquid crystal display (“LCD”) or Ferroelectric LiquidCrystal on Silicon (“FLCOS”) display screen. The display screen can besized such that a user can readily read numbers, lettering, and/orsymbols displayed on the display screen while performing a medicalprocedure. In an embodiment, the display 24 comprises a Quarter VideoGraphics Array (“QVGA”) Thin Film Transistor (“TFT”) LCD screen. Othertypes of display screens can also be used, as can other shapes, sizes,and locations for the display 24 on the surgical orientation device 12.

The surgical orientation device 12 can further comprise at least oneuser input device 26. The at least one user input device 26 can comprisea plurality of buttons located adjacent the display 24. The buttons canbe activated, for example, by a finger, hand, and/or instrument toselect a mode or modes of operation of the device 12, as discussedfurther below. In a preferred arrangement, the at least one user inputcomprises three buttons located underneath the display 24 as illustratedin FIG. 7. In other embodiments, the user input device 26 is a separatecomponent from the housing 20. For example, the user input device 26 cancomprise a remote input device coupled to the surgical orientationdevice 12 via a wired or wireless connection. In yet other embodiments,the user input device 26 comprises a microphone operating in conjunctionwith a speech recognition module configured to receive and processverbal instructions received from a user.

As discussed below in connection with Figures ***, the surgicalorientation device 12 includes a user interface with which a cliniciancan interact during a procedure. In one embodiment, the display 24 andat least one user input 26 can form a user interface. The user interfaceallows a surgeon, medical personnel, and/or other user to operate thesurgical orientation device 12 with ease, efficiency, and accuracy.Specific examples and illustrations of how the user interface canoperate in conjunction with specific methods are disclosed furtherherein.

FIGS. 8 and 9 show a back side 27 of the surgical orientation device 12.The back side 27 can include an attachment structure or structures 28,as well as a gripping feature or features 29 for facilitating handlingof the surgical orientation device 12. The attachment structures 28 canfacilitate attachment of the surgical orientation device 12 to anotherdevice, such as for example the coupling device 14. In a preferredarrangement, the attachment structures 28 comprise grooves, or channels30, along a portion of the back side of the surgical orientation device12.

The attachment structures 28 can be formed, for example, from protrudingportions of the back side of the surgical orientation device 12, and canextend partially, or entirely, along the back side of the surgicalorientation device 12. The attachment structures 28 can receivecorresponding, or mating, structures from the coupling device 14, so asto couple, or lock, the coupling device 14 to the surgical orientationdevice 12. FIGS. 10A and 10B show top and bottom sides 31 a, 31 b of thesurgical orientation device 12. The surgical orientation device 12 cancomprise optical components 32 that can be located on the top side 31 a,the bottom side 31 b, or the top and bottom sides 31 a, 31 b of thesurgical orientation device 12. The optical components 32 can comprisetransparent windows 34 integrated into the surgical orientation device12. The optical components 32 can be windows that permit visible light(e.g. laser light) to emit from the top side 31 a, the bottom side 31 b,or both the top and bottom sides 31 a, 31 b of the surgical orientationdevice 12. While the embodiment illustrated in FIGS. 10 a and 10 b showstwo windows 34 for transmitting light, other numbers are also possible.Additionally, while the optical components 32 are shown located on thetop and bottom of the surgical orientation device 12, in otherembodiments the optical components 32 can be located in other positionsand/or on other portions of the surgical orientation device 12.

FIG. 11 illustrates a high-level block diagram of an electrical system1100 of the surgical orientation device 12. The electrical system 1100comprises an electronic control unit 1102 that communicates with one ormore sensor(s) 1104, one or more visible alignment indicators 1106, apower supply 1108, a display 1110, external memory 1112, one or moreuser input devices 1114, other output devices 1116 and/or one or moreinput/output (“I/O”) ports 1118.

In general, the electronic control unit 1102 receives input from thesensor(s), the external memory 1112, the user input devices 1114 and/orthe I/O ports 1118 and controls and/or transmits output to the visiblealignment indicators 1106, the display 1110, the external memory 1112,the other output devices 1116 and/or the I/O ports 1118. The electroniccontrol unit 1102 can be configured to receive and send electronic data,as well as perform calculations based on received electronic data. Incertain embodiments, the electronic control unit 1102 can be configuredto convert the electronic data from a machine-readable format to a humanreadable format for presentation on the display 1110. The electroniccontrol unit 1102 comprises, by way of example, one or more processors,program logic, or other substrate configurations representing data andinstructions, which operate as described herein. In other embodiments,the electronic control unit 1102 comprises controller circuitry,processor circuitry, processors, general purpose single-chip ormulti-chip microprocessors, digital signal processors, embeddedmicroprocessors, microcontrollers and/or the like. The electroniccontrol unit 1102 can have conventional address lines, conventional datalines, and one or more conventional control lines. In yet otherembodiments, the electronic control unit 1102 comprises anapplication-specific integrated circuit (ASIC) or one or more modulesconfigured to execute on one or more processors. In certain embodiments,the electronic control unit 1102 comprises an AT91SAM7SE microcontrolleravailable from Atmel Corporation.

The electronic control unit 1102 can communicate with internal memoryand/or the external memory 1112 to retrieve and/or store data and/orprogram instructions for software and/or hardware. The internal memoryand the external memory 1112 can include random access memory (“RAM”),such as static RAM, for temporary storage of information and/or readonly memory (“ROM”), such as flash memory, for more permanent storage ofinformation. In some embodiments, the external memory 1112 includes anAT49BV160D-70TU Flash device available from Atmel Corporation and aCY62136EV30LL-45ZSXI SRAM device available from Cypress SemiconductorCorporation. The electronic control unit 1102 can communicate with theexternal memory 1112 via an external memory bus.

In general, the sensor(s) can be configured to provide continuousreal-time data to the surgical orientation device 12. The electroniccontrol unit 1102 can be configured to receive the real-time data fromthe sensor(s) 1104 and to use the sensor data to determine, estimate,and/or calculate an orientation or position of the surgical orientationdevice 12. The orientation information can be used to provide feedbackto a user during the performance of a surgical procedure, such as atotal knee joint replacement surgery, as described in more detailherein.

In some arrangements, the one or more sensors 1104 can comprise at leastone orientation sensor configured to provide real-time data to theelectronic control unit 1102 related to the motion, orientation, and/orposition of the surgical orientation device 12. For example, the sensormodule 1104 can comprise at least one gyroscopic sensor, accelerometersensor, tilt sensor, magnetometer and/or other similar device or devicesconfigured to measure, and/or facilitate determination of, anorientation of the surgical orientation device 12. In some embodiments,the sensors 1104 can be configured to provide measurements relative to areference point(s), line(s), plane(s), and/or gravitational zero.Gravitational zero, as referred to herein, refers generally to anorientation in which an axis of the sensor is perpendicular to the forceof gravity, and thereby experiences no angular offset, for example tilt,pitch, roll, or yaw, relative to a gravitational force vector. In otherembodiments, the sensor(s) 1104 can be configured to providemeasurements for use in dead reckoning or inertial navigation systems.

In various embodiments, the sensor(s) 1104 comprise one or moreaccelerometers that measure the static acceleration of the surgicalorientation device 12 due to gravity. For example, the accelerometerscan be used as tilt sensors to detect rotation of the surgicalorientation device 12 about one or more of its axes. The one or moreaccelerometers can comprise a dual axis accelerometer (which can measurerotation about two axes of rotation) or a three-axis accelerometer(which can measure rotation about three axes of rotation). The changesin orientation about the axes of the accelerometers can be determinedrelative to gravitational zero and/or to a reference plane registeredduring a tibial or femoral preparation procedure as described herein.

In certain embodiments, a multi-axis accelerometer (such as theADXL203CE MEMS accelerometer available from Analog Devices, Inc. or theLIS331DLH accelerometer available from ST Microelectronics.) detectschanges in orientation about two axes of rotation. For example, themulti-axis accelerometer can detect changes in angular position from ahorizontal plane (e.g., anterior/posterior rotation) of the surgicalorientation device 12 and changes in angular position from a verticalplane (e.g., roll rotation) of the surgical orientation device 12. Thechanges in angular position from the horizontal and vertical planes ofthe surgical orientation device 12 (as measured by the sensor 1104 canalso be used to determine changes in a medial-lateral orientation (e.g.,varus/valgus rotation) of the surgical orientation device 12.

In some arrangements, the sensors 1104 comprise at least one single- ormulti-axis gyroscope sensor and at least one single- or multi-axisaccelerometer sensor. For example, the sensor module 1104 can comprise athree-axis gyroscope sensor (or three gyroscope sensors) and athree-axis accelerometer (or three accelerometer sensors) to providepositional and orientational measurements for all six degrees of freedomof the surgical orientation device 12. In some embodiments, the sensorsprovide an inertial navigation or dead reckoning system to continuouslycalculate the position, orientation, and velocity of the surgicalorientation device 12 without the need for external references

In some embodiments, the sensors 1104 comprise one or moreaccelerometers and at least one magnetometer. The magnetometer can beconfigured to measure a strength and/or direction of one or moremagnetic fields in the vicinity of the surgical orientation device 12.The magnetometer can advantageously be configured to detect changes inangular position about a horizontal plane. In other embodiments, thesensors 1104 comprise one or more sensors capable of determiningdistance measurements. For example a sensor located in the surgicalorientation device 12 can be in electrical communication (wired orwireless) with an emitter element mounted at the end of a measurementprobe. In certain embodiments, the electrical control unit can beconfigured to determine the distance between the sensor and emitter (forexample, an axial length of a measurement probe corresponding to adistance to an anatomical landmark, such as a malleolus).

In other embodiments, the one or more sensors 1104 comprise atemperature sensor to monitor system temperature of the electricalsystem 1100. Operation of some of the electrical components can beaffected by changes in temperature. The temperature sensor can beconfigured to transmit signals to the electronic control unit 1102 totake appropriate action. In addition, monitoring the system temperaturecan be used to prevent overheating. In some embodiments, the temperaturesensor comprises a NCP21WV103J03RA thermistor available from MurataManufacturing Co. The electrical system 1100 can further includetemperature, ultrasonic and/or pressure sensors for measuring propertiesof biological tissue and other materials used in the practice ofmedicine or surgery, including determining the hardness, rigidity,and/or density of materials, and/or determining the flow and/orviscosity of substances in the materials, and/or determining thetemperature of tissues or substances within materials.

In certain embodiments, the sensors 1104 facilitate determination of anorientation of the surgical orientation device 12 relative to areference orientation established during a preparation and alignmentprocedure performed during orthopedic surgery. Further details regardingthe operation of the sensors in conjunction with a total kneereplacement surgery will be discussed below.

The one or more sensors 1104 can form a component of a sensor modulethat comprises at least one sensor, signal conditioning circuitry, andan analog-to-digital converter (“ADC”). In certain embodiments, thecomponents of the sensor module 1104 are mounted on a stand-alonecircuit board that is physically separate from, but in electricalcommunication with, the circuit board(s) containing the other electricalcomponents described herein. In other embodiments, the sensor module isphysically integrated on the circuit board(s) with the other electricalcomponents. The signal conditioning circuitry of the sensor module cancomprise one or more circuit components configured to condition, ormanipulate, the output signals from the sensor(s) 1104. In certainembodiments, the signal conditioning circuitry comprises filteringcircuitry and gain circuitry. The filtering circuitry can comprise onemore filters, such as a low pass filter. For example, a 10 Hz singlepole low pass filter can be used to remove vibrational noise or otherlow frequency components of the sensor output signals. The gaincircuitry can comprise one or more operational amplifier circuits thatcan be used to amplify the sensor output signals to increase theresolution potential of the sensor. For example, the operationalamplifier circuit can provide gain such that a 0 g output results in amidrange (e.g., 1.65 V signal), a +1 g output results in a full scale(e.g., 3.3 V) signal and a −1 g output results in a minimum (0 V) signalto the ADC input.

In general, the ADC of the sensor module can be configured to convertthe analog output voltage signals of the sensor(s) 1104 to digital datasamples. In certain embodiments, the digital data samples comprisevoltage counts. The ADC can be mounted in close proximity to the sensorto enhance signal to noise performance. In certain embodiments, the ADCcomprises an AD7921 two channel, 12-bit, 250 Kiloseconds per Sample ADC.In an arrangement having a 12-bit ADC can generate 4096 voltage counts.The ADC can be configured to interface with the electronic control unit1102 via a serial peripheral interface port of the electronic controlunit 1102. In other embodiments, the electronic control unit 1102comprises an on-board ADC that can be used to convert the sensor outputsignals into digital data counts.

With continued reference to FIG. 11, the visible alignment indicators1106 can comprise one or more lasers, which can be configured to projectlaser light through the optical component or components 32 describedabove. For example, the visible alignment indicators 1106 can comprise aforward laser and an aft laser. The laser light can be used to project apoint, a plane, and or a cross-hair onto a target or targets, includingbut not limited to an anatomical feature or landmark, to providealternative or additional orientation information to a surgeon regardingthe orientation of the orientation device 12. For example, laser lightcan be used to project a plane on a portion of bone to indicate aresection line and a cross-hair laser pattern can be used to ensurealignment along two perpendicular axes. In certain embodiments, thevisible alignment indicators 1106 can be used to determine a distance toan anatomical feature or landmark (for example, a laser distancemeasurement system). For example, the electronic control unit 1102 canproject laser light to a target and a sensor 1104 within the surgicalorientation device can sense the laser light reflected back from thetarget and communicate the information to the electronic control unit.The electronic control unit 1102 can then be configured to determine thedistance to the target. The lasers can be controlled by the electroniccontrol unit 1102 via pulse width modulation (“PWM”) outputs. In certainembodiments, the visible alignment indicators 1106 comprise Class 2Mlasers. In other embodiments, the visible alignment indicators 1106comprises other types of lasers or light sources.

The power supply 1108 can comprise one or more power sources configuredto supply DC power to the electronic system 1100 of the surgicalorientation device 12. In certain embodiments, the power supply 1108comprises one or more rechargeable or replaceable batteries and/or oneor more capacitive storage devices (for example, one or more capacitorsor ultracapacitors). In other embodiments, power can be supplied byother wired and/or wireless power sources. In preferred arrangements,the power supply 1108 comprises two AA alkaline, lithium, orrechargeable NiMH batteries. The surgical orientation device 12 can alsoinclude a DC/DC converter to boost the DC power from the power supply toa fixed, constant DC voltage output (e.g., 3.3 volts) to the electroniccontrol unit 1102. In some embodiments, the DC/DC converter comprises aTPS61201DRC synchronous boost converter available from TexasInstruments. The electronic control unit 1106 can be configured tomonitor the battery level if a battery is used for the power supply1108. Monitoring the battery level can advantageously provide advancenotice of power loss. In certain embodiments, the surgical orientationdevice 12 can comprise a timer configured to cause the surgicalorientation device 12 to temporarily power off after a predeterminedperiod of inactivity and/or to permanently power off after apredetermined time-out period.

As discussed above, the display 1110 can comprise an LCD or other typescreen display. The electronic control unit 1102 communicates with thedisplay via the external memory bus. In certain embodiments, theelectronic system 1100 comprises a display controller and/or an LEDdriver and one or more LEDs to provide backlighting for the display1110. For example, the display controller can comprise an LCD controllerintegrated circuit (“IC”) and the LED driver can comprise a FAN5613 LEDdriver available from Fairchild Semiconductor International, Inc. Theelectronic control unit 1102 can be configured to control the LED drivervia a pulse width modulation port to control the brightness of the LEDdisplay. For example, the LED driver can drive four LEDs spaced aroundthe display screen to provide adequate backlighting to enhancevisibility. The display can be configured to display one or moreon-screen graphics. The on-screen graphics can comprise graphical userinterface (“GUI”) images or icons. The GUI images can includeinstructive images, such as illustrated surgical procedure steps, orvisual indicators of the orientation information received from thesensor(s) 1104. For example, the display can be configured to displaydegrees and either a positive or negative sign to indicate direction ofrotation from a reference plane and/or a bubble level indicator to aid auser in maintaining a particular orientation. The display can also beconfigured to display alphanumeric text, symbols, and/or arrows. Forexample, the display can indicate whether a laser is on or off and/orinclude an arrow to a user input button with instructions related to theresult of pressing a particular button.

With continued reference to FIG. 11, the user input device(s) 1114 cancomprise buttons, switches, a touchscreen display, a keyboard, ajoystick, a scroll wheel, a trackball, a remote control, a microphone,and the like. The user input devices 1114 can allow the user to enterdata, make selections, input instructions or commands to the surgicalorientation device 12, verify a position of the surgical orientationdevice 12, turn the visible alignment indicators 1106 on and off, and/orturn the entire surgical orientation device 12 on and off. The otheruser output devices 1116 (i.e. other than the display 1110) can comprisean audio output, such as a speaker, a buzzer, an alarm, or the like. Forexample, the audio output can provide a warning to the user when aparticular condition occurs. The output devices 1116 can also comprise avisible output, such as one or more LED status or notification lights(for example, to indicate low battery level, an error condition, etc.).The audio output can comprise different patterns, tones, cadences,durations, and/or frequencies to signify different conditions or events.In other embodiments, output from the electronic control unit 1102 canbe sent to external display devices, data storage devices, servers,and/or other computing devices (e.g., via a wireless networkcommunication link).

The I/O ports 1118 of the electronic control unit 1102 can comprise aJTAG port and one or more serial communication ports. The JTAG port canbe used to debug software installed on the electronic control unit 1102during testing and manufacturing phases. The JTAG port can be configuredsuch that it is not externally accessible post-manufacture. The serialcommunication ports can include a Universal Serial Bus (“USB”) portand/or one or more universal asynchronous receiver/transmitters (“UART”)ports. At least one of the UART ports can be accessible externallypost-manufacture. The external UART port can be an infrared (“IR”)serial port in communication with an infrared (“IR”) transceiver. The IRserial port can be used to update the software installed on theelectronic control unit 1102 post-manufacture and/or to test theoperation of the electronic control unit 1102 by outputting data fromthe electronic control unit 1102 to an external computing device via anexternal wireless connection. Other types of I/O ports are alsopossible.

As described above, the sensor(s) 1104 can comprise one or moreaccelerometers. Accelerometers can measure the static acceleration ofgravity in one or more axes to measure changes in tilt orientation. Forexample, a three-axis accelerometer can measure the static accelerationdue to gravity along three orthogonal axes, as illustrated in FIG. 12A.A two-axis accelerometer can measure the static acceleration due togravity along two orthogonal axes (for example, the x and y axes of FIG.12A). The output signals of an accelerometer can comprise analog voltagesignals. The output voltage signals for each axis can fluctuate based onthe fluctuation in static acceleration as the accelerometer changes itsorientation with respect to the gravitational force vector. In certainembodiments, an accelerometer experiences static acceleration in therange from −1 g to +1 g through 180 degrees of tilt (with −1 gcorresponding to a −90 degree tilt, 0 g corresponding to a zero degreetilt, and +1 g corresponding to a +90 degree tilt. The accelerationalong each axis can be independent of the acceleration along the otheraxis or axes.

FIG. 12B illustrates a measured acceleration along each of the threeaxes of a three-axis accelerometer in six different orientationpositions. TOP and BOTTOM labels, as well as a circle indicating Pin 1of the accelerometer, have been included to aid in determining thevarious orientations. A gravitational force reference vector isillustrated as pointing straight down toward the Earth's surface. Atpositions A and B, the x-axis and the y-axis of the accelerometer areperpendicular to the force of gravity and the z-axis of theaccelerometer is parallel to the force of gravity; therefore, the x andy acceleration components of static acceleration due to gravity atpositions A and B are 0 g and the z component of static acceleration dueto gravity at positions A and B is +1 g and −1 g, respectively. Atpositions C and E, the x-axis and the z-axis of the accelerometer areperpendicular to the force of gravity and the y-axis is parallel to theforce of gravity; therefore, the x and z acceleration components ofstatic acceleration due to gravity at positions C and E are 0 g and they component of static acceleration due to gravity at positions C and Eis +1 g and −1 g, respectively. At positions D and F, the y-axis andz-axis are perpendicular to the force of gravity and the x-axis isparallel to the force of gravity; therefore, the y and z accelerationcomponents of static acceleration due to gravity at positions D and Fare 0 g and the x component of static acceleration due to gravity atpositions D and F is +1 g and −1 g, respectively. A dual-axisaccelerometer operates in the same manner but without the z component.In certain arrangements, a three-axis accelerometer can be used as atiltmeter to measure changes in orientation about two axes.

Multi-axis accelerometers can be conceptualized as having a separateaccelerometer sensor for each of its axes of measurement, with eachsensor responding to changes in static acceleration in one plane. Incertain embodiments, each accelerometer sensor is most responsive tochanges in tilt (i.e., operates with maximum or optimum accuracy and/orresolution) when its sensitive axis is substantially perpendicular tothe force of gravity (i.e., when the longitudinal plane of theaccelerometer sensor is parallel to the force of gravity) and leastresponsive when the sensitive axis is parallel to the force of gravity(i.e., when the longitudinal plane of the accelerometer sensor isperpendicular to the force of gravity). FIG. 12C illustrates the outputof the accelerometer in g's as it tilts from −90 degrees to +90 degrees.As shown, the tilt sensitivity diminishes between −90 degrees and −45degrees and between +45 degrees and +90 degrees (as shown by thedecrease in slope). This resolution problem at the outer ranges of tiltmotion makes the measurements much less accurate for tilt measurementsover 45 degrees. In certain embodiments, when the mounting angle of thesurgical orientation device 12 is known, the sensor(s) 1104 can bemounted to be offset at an angle such that the accelerometer sensors canoperate in their more accurate, steeper slope regions. For example, foruse during the knee surgery preparation procedures described herein, thesensor(s) 1104 can be mounted at approximately a 22-degree anglerelative to the anterior-posterior axis of the surgical orientationdevice 12 to account for a predetermined range of motion of the surgicalorientation device 12 about the flexion/extension axis during theprocedures. It should be appreciated by one of ordinary skill in the artthat the accelerometer can be mounted at acute angles other thanapproximately 22 degrees. In other arrangements, the sensor(s) 1104 canbe mounted to be offset to account for a predetermined range of motionabout other axes of rotation as well. In yet other arrangements, forexample, when a three-axis accelerometer is used, the accelerometersensor(s) can be mounted in parallel with the anterior-posterior axis ofthe surgical orientation device 12. In one three-axis accelerometerarrangement, a handoff system can be incorporated to ensure that theaccelerometer sensors with the most accurate reading (e.g., <45 degrees)are being used at each orientation position. The handoff system canemploy hysteresis to avoid “bouncing” phenomena during the handoffsbetween the accelerometer sensors.

FIG. 12D illustrates the inside of the surgical orientation device 12,according to an embodiment of the invention. The surgical orientationdevice 12 can comprise one or more circuit boards and/or other circuitrycapable of installation within the surgical orientation device 12. Asillustrated, the surgical orientation device 12 can comprise a sensorboard 36A and a main board 36B. The components of the sensor module(including the sensor(s) 1104) can be mounted on the sensor board 36Aand the other components of the electrical system 1100 are mounted onthe main board 36B. The sensor board 36A can comprise one or moresensors 40 (e.g., sensor(s) 1104 as described above). In alternativeembodiments, the sensor board 36A and the main board 36B can be combinedinto a single circuit board. The sensor board 36A and the main board 36Bcan comprise rigid or flexible circuit boards. The sensor board 36A andthe main board 36B can be fixedly or removably attached to the outerhousing 20.

As illustrated, the sensor board 36A is mounted at an approximately22-degree angle relative to a plane extending longitudinally through thehousing 20, which can be parallel to or correspond to ananterior-posterior axis of the main board 36B. As described above,mounting the sensor board 36A at an offset angle can enable the one ormore sensors to operate in the regions of maximum or optimumsensitivity, accuracy and/or resolution. The particular mounting offsetangle can be selected based on a range of motion of the surgicalorientation device 12 during a particular orthopedic procedure. Forexample, during the tibial preparation procedures described herein, thesurgical orientation device 12 can be aligned with the coronal plane ofthe tibia with the leg in flexion and during the femoral preparationprocedures described herein, the surgical orientation device 12 can bealigned to the leg in extension. Accordingly, the mounting offset angleis set at approximately 22 degrees to keep the orientation of thesensors from getting too close to the less accurate, low resolutionrange when the surgical orientation device 12 is positioned in the twoflexion/extension orientations. As shown in FIG. 12D, the surgicalorientation device 12 can include two AA batteries 38 as the powersupply 1110 for providing power to the surgical orientation device 12.The surgical orientation device 12 also can include lasers 42 as thevisible alignment indicators 1106 described above.

FIG. 12E is a high-level flowchart of an exemplary conversion processfor converting an analog voltage output signal of a multi-axisaccelerometer into an angle degree measurement for presentation on thedisplay 24. Although the steps are described as being implemented withhardware and/or software, each of the steps illustrated in FIG. 12E canbe implemented using hardware and/or software. It should be appreciatedthat a similar conversion process can be performed for any other type ofsensor or for multiple separate sensors without departing from thespirit and/or scope of the disclosure.

For each axis of rotation measured (e.g., pitch and roll), themulti-axis accelerometer can continuously output an analog voltagesignal. At Block 1205, the signal conditioning circuitry of the sensormodule can filter the analog output voltage signal (e.g., with a lowpass filter) to remove noise from the signal that may be present due tothe high sensitivity of the multi-axis accelerometer. At Block 1210, thesignal conditioning circuitry amplifies, or boosts, the output voltagesignal, for example, via the gain circuitry described above.

At Block 1215, the ADC can convert the continuous analog voltage signalinto a discrete digital sequence of data samples, or voltage counts. Incertain embodiments, the ADC can sample the analog voltage signal onceevery two milliseconds; however, other sampling rates are possible. Incertain embodiments, the analog voltage signal is oversampled. At Block1220, the electronic control unit 1102 can generate a stable data pointto be converted to an angle measurement. The electronic control unit1102 can apply a median filter to the sampled data to eliminate outliers(e.g., spikes) in the data. For example, the electronic unit 1102 canuse an 11-sample median filter to generate the middle value from thelast 11 samples taken. The output of the median filter can then be fedinto a rolling average filter (for example, a 128 sample rolling averagefilter). The rolling average filter can be used to smoothe or stabilizethe data that is actually converted to an angle measurement. Theelectronic control unit 1102 can implement Blocks 1215 and 1220 using afinite impulse response (“FIR”) or an infinite impulse response (“IIR”)filter implemented in a software module.

At Block 1225, the electronic control unit 1102 can convert the voltagecount data to an angle measurement in degrees. In performing theconversion, the electronic control unit 1102 can be configured to applya calibration conversion algorithm based on a calibration routineperformed during a testing phase prior to sale of the surgicalorientation device 12. The calibration conversion can be configured toaccount for unit-to-unit variations in components and sensor placement.The calibration routine can be performed for each axis being monitoredby the multi-axis accelerometer. The calibration conversion can compriseremoving any mechanical or electrical offsets and applying anappropriate gain calibration for a positive or negative tilt.

As described above, the ADC can comprise an ADC with 12-bit resolution,which provides 4096 distinct voltage counts, wherein a −90 degree tiltcorresponds to 0 counts (−2048 signed counts), a zero degree tiltcorresponds to 2048 counts (0 signed counts), and a +90 degree tiltcorresponds to 4096 counts (+2048 signed counts). The tilt angle foreach axis (e.g., pitch and roll) of the multi-axis accelerometer can becalculated from the voltage count data based on standard trigonometricrelationships as the arc sin of the acceleration component in eachparticular axis. In arrangements in which the electronic control unit1102 applies the calibration conversion, the tilt angle for each axiscan be calculated as follows:

$\begin{matrix}{{{ANGLE} = {a\; {\sin\left\lbrack \frac{\left. {\begin{pmatrix}{{{SignedADC}\mspace{14mu} {Counts}} +} \\{OFFSET}\end{pmatrix} \times {GAIN}} \right)}{2048} \right\rbrack}}},} & (12.1)\end{matrix}$

where OFFSET corresponds with a zero offset of the surgical orientationdevice 12 determined during the calibration routine and GAIN correspondswith a ratiometric value determined during the calibration routine, withone GAIN value being used for negative tilt angles and a different GAINvalue being used for positive tilt angles.

Also at Block 1225, in arrangements where a dual-axis accelerometer isused, the electronic control unit 1102 can be configured to adjust thepitch angle (x axis) calculation to account for the mounting offsetangle (described above) of the dual-axis accelerometer relative to theouter housing 20 of the surgical orientation device 20. The result ofBlock 1225 is an absolute angle for each axis of rotation (e.g., pitch,roll) being monitored by the dual-axis accelerometer. The absolute pitchand roll angles can be used to calculate orientation measurements of thesurgical orientation device 12, such as a flexion-extension angle and avarus/valgus angle (as described in more detail below).

Orientation measurements for the surgical orientation device 12 can bedetermined based on a wide variety of reference frames in conjunctionwith any of a variety of surgical procedures. For example, when used inconjunction with a total knee replacement arthroscopic procedure, areference frame can be established as shown in FIG. 12F.

As illustrated in FIG. 12F, the reference frame 1200 comprises threeorthogonal axes (labeled x, y and z) having a point of origin at thecenter of a patient's knee joint when the patient's left leg is inflexion. The x-axis is illustrated as extending out of the page (in alateral direction from the knee parallel to the horizon). The y-axis isillustrated as extending along a coronal plane of the tibia. The z-axisis illustrated as extending straight out from the knee at an offset of90 degrees from the coronal plane of the tibia. As described herein, aflexion/extension rotation, or posterior-anterior pitch rotation,corresponds to rotation about the x-axis of the reference frame 1200 anda varus/valgus rotation, or a medial-lateral rotation, corresponds torotation about the z-axis of the reference frame 1200. A roll rotation,as described herein, corresponds to rotation about the y-axis of thereference frame 1200. During the performance of alignment procedures inwhich the leg is fully extended, the x-axis maintains the sameorientation and the y and z axes rotate toward the mechanical axis ofthe leg about the x axis.

As described above, a sensor 40 (e.g., a multi-axis accelerometer) canbe configured to measure changes in angular position from a horizontalaxis (e.g., pitch) and a vertical axis (e.g., roll). In performing themethods described herein, the surgical orientation device 12 can bemounted such that the pitch measurement of the sensor 40 corresponds torotation about the x axis (e.g., flexion/extension rotation) of thereference frame 1200 and such that the roll measurement of the sensor 40corresponds with rotation about the y axis of the reference frame 1200.

In arrangements employing the use of the tibial preparation system 310,the flexion/extension angle is calculated according to formula 12.1above. In arrangements where a dual-axis accelerometer is used, thecalculated flexion/extension angle can be adjusted to account for amounting offset angle or can be compared to a referenceflexion/extension orientation plane to generate a relative anglemeasurement. A relative flexion/extension angle can be generated bysubtracting a reference flexion/extension angle stored in memory fromthe absolute measured flexion/extension angle. In certain embodiments,the reference flexion/extension angle corresponds with the orientationof the coronal plane of the tibia.

In arrangements employing the use of the tibial preparation system 310,the varus/valgus angle can be derived based on the assumption that thepitch angle of the accelerometer, which corresponds with theflexion/extension angle of the surgical orientation device 12, is fixedand known (e.g., the surgical orientation device 12 is mounted to anextramedullary alignment guide 314 that can only be rotated laterally ormedially on a plane of fixed pitch) and on the assumption that therotation angle of the roll sensor of the accelerometer was substantiallyzero degrees when the fixed pitch angle measurement (e.g., the referenceflexion/extension angle) was registered, or recorded. Based on these twoassumptions, the varus/valgus angle can be calculated as follows:

$\begin{matrix}{{{Varus}\text{/}{Valgus}\mspace{14mu} {Angle}} = {{arc}\; {\sin \left\lbrack \frac{\sin ({rollangle})}{\sin ({fixedpitchangle})} \right\rbrack}}} & (12.2)\end{matrix}$

where the roll angle is the current absolute roll angle being measuredby the roll sensor of the accelerometer. A relative varus/valgus anglecan be generated by subtracting a reference varus/valgus angle stored inmemory from the absolute measured varus/valgus angle. In certainembodiments, the reference varus/valgus angle corresponds with theorientation of the sagittal plane of the tibia.

In arrangements where the tibial preparation systems 410 and 610 areused, the flexion/extension angle and the varus/valgus angle can becalculated as follows:

$\begin{matrix}{\mspace{79mu} {{{Varus}\text{/}{Valgus}\mspace{14mu} {Angle}} = {{arc}\; {\sin \left\lbrack \frac{\sin ({rollangle})}{\sin ({pitchangle})} \right\rbrack}}}} & (12.3) \\{\left. {{{Flexion}\text{/}{Extension}\mspace{14mu} {Angle}} = {{arc}\; {\sin \left\lbrack \frac{\sin ({rollangle})}{\sin\left( {{Varus}\text{/}{ValgusAngle}} \right)} \right\rbrack}}} \right\rbrack,} & (12.4)\end{matrix}$

where the roll angle is the current absolute roll angle being measuredby the accelerometer and the pitch angle is the current absolute pitchangle being measured by the accelerometer. As discussed above, thesecalculations can also be adjusted based on a calibration conversion or amounting offset angle.

In certain embodiments, the above calculations can be performed bysoftware modules executed by the electronic control unit 1102. In otherembodiments, the electronic control unit 1102 can generate the anglemeasurements using data stored in one or more look-up tables (“LUT”s).In other embodiments, other calculations can be derived based on thetype of sensor or sensors used, the procedure being performed, and/orthe reference frame being employed.

In certain embodiments, the electronic control unit 1102 can perform astabilization routine, process, or algorithm to assess or determine thestability, or reliability, of the calculated angle measurements. Forexample, the electronic control unit 1102 can keep a history of the last100 ms of calibrated sample data for each axis being monitored by thesensor(s) 40. Each time a new sample is added to the 100-sample history,a maximum and minimum value is determined for the 100-sample data set.The electronic control unit 1102 can then determine a delta differencebetween the maximum and minimum values. The electronic control unit 1102can then compare the delta difference between the maximum and minimumvalues to a threshold. If the delta difference is lower than thethreshold, then the data is considered to be stable and it is stored inmemory (e.g., external memory 1112) and time-stamped. If the deltadifference is greater than the threshold, then the data is considered tobe unstable. When retrieving an angle reading to display to the user,the electronic control unit 1102 can be configured to transmit the laststable data reading (assuming it is not too old) to the display 1110instead of the current unstable reading. If the last stable angleexceeds a time threshold, the unstable angle reading can be displayedalong with a visual indication notifying the user that the angle readingis unstable. For example, a red “shaky hand” icon or graphical userinterface image can be displayed on the display screen.

2. Surgical Orientation Device with a Disposable Portion which AllowsInner Components to be Reused in a Sanitary Manner

In one embodiment, a surgical orientation device can be provided with adisposable housing. This arrangement can maximize reuse of internalcomponents while maintaining the cleanliness of the device. FIG. 13shows an embodiment of a surgical orientation device 12 a whichcomprises a disposable outer housing 21. The disposable outer housing 21can include, or be releasably attached to, a cover 44. The cover 44 canbe in the form of a latch, flap, zipper, plastic-zip fastener, or othersimilar structure which covers and/or seals an opening in the disposableouter housing 21. The cover 44 can be pivotally connected to a portionof the disposable outer housing 21, such that when the cover 44 is swungopen or removed, visual inspection and removal/insertion of interior,reusable components (e.g. the electronic control unit 1102, display 24,optical components 32) of the surgical orientation device 12 a isprovided.

The disposable outer housing 21 can be manufactured and packaged in asterile state and can provide a sterile barrier between the reusablecomponents inside the surgical orientation device 12 and their outsideenvironment. Thus, once the surgical orientation device 12 has beenused, the disposable outer housing 21 can be discarded or destroyed, andthe interior, reusable components can be used again.

The disposable outer housing 21 can also be manufactured such that itengages and/or receives one or more interior reusable components of thesurgical orientation device 12. Preferably these components are receivedwithin the housing 21 without the interior reusable componentscontacting any outside surface of the disposable outer housing 21,thereby protecting the outside surfaces of the disposable outer housing21 from contact with the interior reusable components. A separate,sterile shield can provide a temporary barrier between the sterilehousing and non-sterile surgical orientation device 12 during insertionto prevent accidental contact between the surgical orientation device 12and outside surfaces of the housing. Once the surgical orientationdevice 12 is inserted the shield can be removed and discarded allowingthe door to be closed.

The disposable outer housing 21 can contain slots or grooves on one ormore interior walls of the disposable outer housing 21 to enable theinterior reusable components, or a combined set of interior reusablecomponents in the form of a reusable assembly, to be positioned or setwithin the disposable outer housing 21. For example, the reusablecomponents or assembly can contain slots or grooves which mate with theslots or grooves of the disposable outer housing 21. This matingarrangement can minimize contact between more delicate features of thereusable components (e.g. a circuit board) and the inside surfaces ofthe disposable outer housing 21. In some embodiments the inside of thedisposable outer housing 21 and the outside of the interior reusablecomponents or assembly can be tapered to allow easy, low precisioninsertion of the interior reusable components or assembly but providesecure mating once the disposable outer housing 21 and the reusableinterior components or assembly are fully engaged. Electrical contactbetween the surgical orientation device 12 and housing can be providedby spring loaded probes and conductive contacts. The disposable housing21 can include touch screen for user interface. (e.g. an LCD display canstill be part of the SOD). The disposable housing 21 can be packagedwith disposable batteries so users don't have to deal with recharging ofbatteries.

In yet other configurations, the interior reusable components, assembly,and/or disposable outer housing 21 of the device can contain othermating features, including but not limited to clamps or adaptors, whichfacilitate sanitary handling of the surgical orientation device 12.

The disposable outer housing 21 can also contain one or more sheets ofmaterial, such as a thin plastic layer, temporarily affixed to one ormore of its outside surfaces (for example by a weak adhesive),sufficient to protect the disposable outer housing 21 from contaminationby the reusable interior components or assembly during the process ofengaging the disposable outer housing 21 to the reusable interiorcomponents or assembly. The sheets of material temporarily affixed tothe disposable outer housing 21 can be removed following the engagementof the disposable outer housing 21 to the reusable interior componentsor assembly.

In a preferred arrangement, the disposable outer housing 21 can includea transparent section or sections (e.g. a thin plastic membrane) whichcovers both the display 24 and user inputs 26. This section or sectionsof the disposable housing 21 can be manufactured to allow the user tomanipulate the user interface elements by pressing against this sectionor sections of the disposable housing 21. For example, the disposableouter housing 21 can include a touch-sensitive overlay which covers thedisplay 24 to enable the display 24 of the surgical orientation device12 to be operated as a touch screen. The surgical orientation device 12can include an electrical interface, for example probes or slidingcontacts, between the disposable and re-usable elements of the touchscreen (i.e. the transparent sections of the disposable outer housing 21and the display 24) to enable the transfer of information, electricityand/or other energy between the disposable outer housing 21 and thedisplay 24.

With continued reference to FIGS. 12 and 13, the batteries 38 can be ineither or both of the reusable and disposable portion or portions of thesurgical orientation device 12. If the batteries 38 are contained in thedisposable outer housing 21, the surgical orientation device 12 cancontain one or more transmission media, connectable between the reusableinterior elements or assembly and the disposable outer housing 21,capable of conducting power from the batteries in the disposable outerhousing 21 to the reusable interior components or assembly that requirespower for the surgical orientation device's operation.

3. Device for Coupling a Surgical Orientation Device to OrthopedicFixtures

A device can be provided which can be used to couple a surgicalorientation device to one or more orthopedic fixtures. For example,FIGS. 2 and 14 show a coupling device 14. The coupling device 14 cancomprise a housing 46, cam mechanism 48, and a surgical orientationdevice attachment mechanism 50. The coupling device 14 can be usedgenerally to attach two surgical instruments and/or components together.For example, in the tibial preparation system 10, the coupling device 14can be used to couple the surgical orientation device 12 to theuniversal jig 16.

FIG. 15 shows the housing 46, which can be made out of plastic or othersuitable material including but not limited to polypropylene or PET. Thehousing 46 can include openings and/or slots 52 for insertion of the cammechanism 48 and surgical orientation device attachment mechanism 50.The housing 46 can further include an elongate portion 54, which can beinserted into the grooves or channels 30 along the back portion of thesurgical orientation device 12 described above.

FIG. 16 shows the cam mechanism 48, which can comprise a handle 56 withan off-center cam 58 at one end. The off-center cam 58 can be pivotallyattached to an arm 60. The arm 60 can include a pin or pivot mechanismwhich is insertable into an opening 52 of the housing 46.

FIG. 17 shows the coupling device 14 fully assembled. The couplingdevice 14 can be used to frictionally engage and hold onto a surgicalinstrument or component. For example, as the handle 56 is rotated, thearm 60 can swing into a position such that an end 62 of the arm 60 isfrictionally engaged with or clamps onto a portion of a surgicalinstrument or component extending through the opening 64. The surgicalinstrument or component can extend between structures 77 of the housing46. such that as the arm 60 swings, the end 62 can contact the surgicalinstrument or component and press it firmly against the structure 77,thereby at least partially locking the surgical instrument or componentto the coupling device 14.

With reference again to FIG. 16, the surgical orientation deviceattachment mechanism 50 can comprise a knob 66. The knob 66 can beattached to an arm 68. The arm 68 can be attached to a rotatablestructure 70. The rotatable structure 70 can comprise a pin 72 which canbe inserted into an opening 62 of housing 46. The rotatable structure 70can also comprise a protrusion 74. As the knob 66 is pushed, and/orturned, the protrusion 74 can pivot about the pin 72.

With reference to FIGS. 8, 9, 14, and 16, the surgical orientationdevice 12 can be securely attached to the coupling device 14. To attachthe surgical orientation device 12 to the coupling device 14, theelongate portion 54 of the coupling device 14 can be inserted into thegrooves or channels 30 along the back of the surgical orientation device12. Once a portion of the elongate portion 54 is inside the grooves orchannels 30, the surgical orientation device attachment mechanism 50 canbe used to secure the surgical orientation device 12 to the couplingdevice 14. For example, the knob 66 can be pulled, and/or turned, suchthat the protrusion 74 pivots about the pin 72, and moves into a groove76 shown in FIGS. 8 and 9. Once inside the groove 76, the protrusion 74can inhibit the surgical orientation device 12 from slipping off ofand/or becoming removed from, the coupling device 14. In someembodiments, the knob 66 and/or protrusion 74 can be biased by acompressive member (e.g. spring) housed in the housing 46 to facilitateattachment of the coupling device 14 to the surgical orientation device12. For example, the protrusion 74 can be biased towards a lockingposition in which the protrusion is moved towards the groove 76 shown inFIGS. 8 and 9. In some embodiments, the knob 66 can be pushed and/orturned to release the surgical orientation device 12 from the couplingdevice 14.

While the coupling device 14 described above can be used to attachand/or couple the surgical orientation device 12 with the universal jig16, other methods and devices for attaching and/or coupling thecomponents of the tibial preparation system 10 are also possible.

FIG. 17 a shows another embodiment of a coupling device 14′. Thecoupling device 14′ can be similar to the coupling device 14 describedabove, and can include an elongate protrusion 54′, a handle 56′, an arm60′, and a knob 66′. The knob 66′ can comprise a lever-like structurewhich can pivot in order to lock and unlock a portion of the couplingdevice.

4. Orthopedic Fixture for Orienting a Surgical Orientation Device inMultiple Degrees of Freedom

An orthopedic fixture can be provided which can have a moveable portionor portions which are used to orient a surgical orientation device. Thesurgical orientation device can be oriented in multiple degrees offreedom. For example, FIGS. 2, 18, and 19 show an orthopedic fixture inthe form of a universal jig 16. The universal jig 16 can comprise a basemember 78, a posterior/anterior adjustment block 80, a varus/valgusadjustment block 82, and a cutting block 84 (e.g. an anterior block forplacement or attachment along an anterior surface of the tibia). Thesecomponents provide for multiple degrees of freedom of operation of amoveable portion of the jig 16 such that devices coupled therewith(e.g., the surgical orientation device 12) can be moved to a variety oforientations during the procedure.

a. Base Member for Providing an Anchored or Fixed Initial Position of anOrthopedic Fixture

A base member can be provided that anchors an orthopedic fixture and/orprovides a fixed initial position of a moveable orthopedic fixture. Forexample, a base member 78 can comprise a structure that is rigidlyand/or fixedly attached to an anatomical structure. The base member 78can be attached to an anterior surface of a patient's tibia. In apreferred arrangement, the base member 78 can comprise at least one basemember attachment opening 86. For example, the base member 84 cancomprise two base member attachment openings 86. Attachment openings,apertures, and/or holes as described herein with respect to tibialpreparation system 10 and other systems described herein, can comprisebores, non-threaded holes, threaded holes, and/or other types of holesor openings which extend partially or entirely through a structure.

For example, the base member attachment openings 86 can extend entirelythrough the base member 78. Each of the base member attachment openings86 can be configured to receive a fastening device, such as for examplea screw, to anchor the base member 78 into a bone or other anatomicalstructure and fix the base member 78 relative to the bone or anatomicalstructure.

The base member 78 can further comprise a base member receiving opening88. The receiving opening 88 can be located along an anterior side ofthe base member 78, and can be sized and shaped so as to receive a pinof the varus/valgus adjustment block 82. The receiving opening 88 canextend entirely or partially through the base member 78, and in someembodiments can be partially or entirely threaded.

The base member 78 can further comprise a base member pin 90. Pins, asdescribed herein with respect to tibial preparation system 10 and othersystems described herein, can be solid, threaded, formed of plastic,metal, or other material, comprise linear bearings, and/or have shapessizes, and configurations other than those shown and/or described.

The pin 90 can extend through an opening or openings 91 of the basemember 78, and can be sized and shaped so as to be inserted through acut-out 95 of the posterior/anterior adjustment block 80. The pin 90 canbe partially or entirely threaded, and can include a knobbed portion 90a on one end which can be gripped and turned by a user.

The base member 78 can further comprise an elongate base member rod 92.The elongate base member rod 92 can extend distally beneath the pins 90,96, and can include a brace-like structure 94 on a distal end thereof.The brace-like structure 94 can be curved, and used to brace and/or holdthe universal jig 16 against the patient's skin overlying the tibiaduring the knee replacement procedure. The base member rod 92 andstructure 94 can provide a stabilizing force against a portion of thetibia. For example, the structure 94 can be placed around, or wrapped,against the skin near a proximal portion of the tibia. The universal jig16 can, while being anchored or moved as described herein, experience aforce or forces which can tend to cause the universal jig 16 as a wholeto twist or rotate. The structure 94 can at least partially absorb theseforces by bracing itself against the tibia. For example, the structure94 can minimize a torquing motion of the universal jig 16 while ananchoring pin or pins are being inserted through the base member andinto the tibia. Also, once the universal jig 16 is locked in positionfor resection it can resist torquing during resection caused by pressureof a cutting tool in a slot of the cutting block 84. This can improveaccuracy of resection. The base member rod 92 and structure 94 can beadjusted accordingly to account for these forces. For example, thestructure 94 can be rotated about the end of the base member rod 92,and/or be made of material capable of withstanding anticipated forces.Additionally or alternatively, the base member rod 92 can be configuredto adjust distally so as to extend or shorten, depending on a desiredlocation for the structure 94.

b. Device for Adjusting a Posterior/Anterior Slope of a Cutting Block

A device can be provided which can be used to adjust the orientation ina sagittal plane of a surgical orientation device and/or cutting block.For example, and with continued reference to FIGS. 2, 18, and 19, theposterior/anterior adjustment block 80 of universal jig 16 can comprisea structure which is moveable (e.g. rotatable) in at least one of aposterior and anterior direction.

The posterior/anterior adjustment block 80 can comprise a cutout 95. Thecutout 95 can be sized and shaped so as to generally receive and/orsurround the base member pin 90. The cutout 95 can extend entirelythrough the posterior/anterior adjustment block 80, and can generallyform a cut-out portion of the block 80.

The posterior/anterior adjustment block 80 can further comprise aposterior/anterior adjustment pin 96. The pin 96 can extend through anopening 97 of the posterior/anterior adjustment block 80. One end of thepin 96 can be sized and shaped so as to contact and/or be insertedwithin an opening 97 a of the varus/valgus adjustment block 82. The pin96 can be partially or entirely threaded, and can include a knobbedportion 96 a on one end which can be gripped and turned by a user.

The posterior/anterior adjustment block 80 can further compriseposterior/anterior adjustment block hinge openings 98. The hingeopenings 98 can be sized and shaped to receive a pin-like structure. Theposterior/anterior adjustment block 80 can pivot about the pin-likestructure and/or about an axis extending through the hinge openings 98when the knob 96 a on the end of the posterior/anterior adjustment blockpin 96 is turned.

The posterior/anterior adjustment block 80 can further comprise anopening 105 and/or structure which can receive and/or affix a portion ofthe cutting block 84 (e.g. rod 104) to the posterior/anterior adjustmentblock 80. By affixing the posterior/anterior adjustment block 80 to thecutting block 84, movement of the posterior/anterior adjustment block 80and cutting block 84 can be linked such that movement of theposterior/anterior adjustment block 80 can cause similar or identicalmovement of the cutting block 80.

The posterior/anterior adjustment block 80 can further comprise aposterior/anterior adjustment block guide rod 99. The guide rod 99 canextend from the posterior/anterior adjustment block 80, and can be sizedand shaped to receive and/or couple with the surgical orientation device12, or coupling device 14.

c. Device for Adjusting a Varus/Valgus Slope of a Cutting Block

A device can be provided which can be used to adjust the orientation ina coronal plane of a surgical orientation device and/or cutting block.For example, and with continued reference to FIGS. 2, 18, and 19, thevarus/valgus adjustment block 82 of universal jig 16 can comprise astructure which is moveable (e.g. rotatable) in at least one of avarus/valgus direction.

The varus/valgus adjustment block 82 can comprise a varus/valgusadjustment block pin 100. The pin 100 can extend through a portion orportions of the varus/valgus adjustment block 82. The pin 100 can bereceived within the base member receiving hole 88, and in someembodiments can be partially or entirely threaded. In some embodimentsthe pin 100 can be unthreaded. The pin 100 can include a pin opening 100a. The pin opening 100 a can receive the same pin-like structurereceived by the hinge openings 98 described above.

When the base member pin 90 is turned, the varus/valgus adjustment block82 can pivot about the pin 100, such that the varus/valgus adjustmentblock 82 pivots in at least one of a varus and valgus direction.

The varus/valgus adjustment block 82 can further include an opening 103along a side surface 101 of the varus/valgus adjustment block 82, whichcan receive the base member pin 90. In some embodiments the opening 103can be threaded or structured in a manner such that turning the knob 90a on the end of the pin 90 in either a clockwise or counterclockwisedirection can cause movement of the varus/valgus adjustment block 82.

With continued reference to FIGS. 2 and 18, movement of the varus/valgusadjustment block 82 can cause movement of the posterior/anterioradjustment block 80. For example, a portion or portions of thevarus/valgus adjustment block 82 can rest within and/or be contacted oneither side by portions of the posterior/anterior adjustment block 80,such that any movement of the varus/valgus adjustment block 82 in avarus or valgus direction likewise causes similar or identical movementof the posterior/anterior adjustment block 80.

d. Cutting Block which can be Oriented in a Posterior/Anterior, and/or aVarus/Valgus, Direction for Bone Resection

A cutting block, or other orthopedic fixture, can be provided for boneresection. The cutting block can be oriented with the aid of a surgicalorientation device, an orthopedic fixture, or a surgical orientationdevice and an orthopedic fixture. For example, and with continuedreference to FIGS. 2, 18, and 19, the cutting block 84 can comprise atleast one opening 102. One opening 102 can comprise, for example, anelongate slit along a width of an upper, or proximal, portion of thecutting block 84 for receiving and guiding a saw, blade, or othercutting tool. Other openings 102 a can extend from an anterior face 84 aof the cutting block 84 towards a posterior face 84 b thereof, and cancomprise holes for insertion of an anchoring pin or pins. In varioustechniques, such pins are extended through the openings 102 a and intoan anterior face of the tibia. The cutting block 84 can also include aprobe 84 for aiding in referencing an anatomical landmark.

As described above, the posterior/anterior adjustment block 80 can becoupled to the cutting block 84 such that movement of theposterior/anterior adjustment block 80 causes similar or identicalmovement of the cutting block 84. For example, the cutting block 84 cancomprise a cutting block guide rod 104. The guide rod 104 can extendfrom the upper, or proximal, portion of the cutting block 84, and can besized and shaped so as to be received within the opening 105 of theposterior/anterior adjustment block 80. The opening 105 can extendthrough the posterior/anterior adjustment block 80 adjacent theposterior/anterior adjustment block hinge holes 98. This opening canreceive the cutting block guide rod 104, and couple theanterior/posterior adjustment block 80 to the cutting block 84 to linkmovement between the posterior/anterior adjustment block 80 and cuttingblock 84. The cutting block 84, as well as other cutting blocksdescribed herein, can in some embodiments be removably attachable to oneor more components of an orthopedic fixture, and can be attached orremoved at various stages of an orthopedic procedure.

5. Target Probes which can be Used to Identify Anatomical Planes or Axes

Target probes can be provided for identifying anatomical planes and/oraxes. For example, and with reference to FIGS. 2 and 20, the at leastone target probe 18 a, 18 b, or other targets or devices, can comprise astructure for contacting an anatomical landmark and serving as a targetfor an emitted laser beam or beams from the surgical orientation device12. For example, in a preferred arrangement, the at least one targetprobe 18 a, 18 b can comprise an elongate member 106 with an anatomicalcontact portion 107 and a target portion 108.

The anatomical contact portion 107 can comprise an end of the elongatemember 106 or other structure configured to contact an anatomicalfeature, such as for example the lateral malleolus. The anatomicalcontact portion 107 can be held against the anatomical feature by hand,can be drilled into the anatomical feature, or can be held againstand/or coupled with the anatomical feature in some another fashion.

The anatomical contact portion 107 can be connected to or integrallyformed with the target portion 108. The target portion 108 can comprisean area on the target probe 18 a, 18 b which, as described furtherherein, is configured to indicate whether the target probe 18 a, 18 b isaligned with the surgical orientation device 12 and/or cutting block 84.For example, the target portion 108 can comprise one or more targetshapes 110, in the form of markings, slits, or other structures. Thetarget shapes 110, if for example in the form of slots, can be wideenough to allow a beam of laser light, such as for example a beam in theform of a plane or a cross-hair beam, to pass through the target shapes110. FIG. 20 illustrates an embodiment of a target probe 18 b with atarget shape 110 in the form of a single slot, and a target probe 18 awith two slots in the form of a cross, for example formed as twoperpendicular lines or slots

The target portion 108 can additionally be adjustable, such that as theanatomical contact portion 107 is held in place against the anatomicallandmark, the target portion 108 can be moved relative to the anatomicallandmark. For example, the target portion 108 can comprise a screw orother element which can be adjusted in order to change the length of thetarget probe 18 a, 18 b. In one embodiment, a device is provided toenable the position of the target portion 108 on the elongate member 106to be adjusted. The device enables the target portion 108 to be movedcloser to or away from the contact portion 106. Such adjustment providesone technique for aligning an orthopedic fixture, a surgical orientationdevice, or an orthopedic fixture and surgical orientation device, with acoronal or sagittal plane.

The target probes 18 a, 18 b can further include a marking or markingswhich indicate a current length of the target probe 18 a, 18 b, and/orindicate the degree or amount of adjustment which has been made to thetarget probe 18 a, 18 b. For example, the target portion 108 cancomprise millimeter markings or other visual indicia corresponding tolengthwise offset along a length of the target portion 108, indicatingadjustments in the length of millimeters.

In some embodiments, the target probes 18 a, 18 b shown in FIG. 20 cancomprise the same target probe. Thus, FIG. 20 can illustrate oppositesides of the same target probe. For example, one side of the targetprobe can have a cross-hair target 110, and the other side of the targetprobe can have a single slot target 110.

6. Additional Sensors for Relative Movement

While the embodiment of the tibia preparation system 10 described aboveis described as having a sensor or sensors 40 located entirely withinthe surgical orientation device 12, in other embodiments the tibiapreparation system 10, or other systems used for joint replacementand/or resection (e.g. for hip and shoulder), can include an additionalsensor or sensors 40. These additional sensors 40 can be located onother surgical components and/or anatomical landmarks. U.S. Pat. No.7,559,931 discloses examples of sensors on multiple surgical componentsand/or anatomical landmarks, and is herein expressly incorporated byreference and made a part of this disclosure. In one embodiment, thetibia preparation system 10 can include an additional sensor 40 locatedon the base member 78, or on the proximal tibia. The additional sensor40 can include a microcontroller and/or communication device (e.g.infrared or other wireless technology (e.g. Bluetooth™)) which can relayinformation from the additional sensor 40 to the electronic control unit1102 of the surgical orientation device 12. This additional sensor orsensors 40 can detect changes in movement of the tibia and/or leg duringa knee replacement procedure, so as to verify whether the patient's leg(which typically is securely held in place during the procedure) hasinadvertently or unintentionally moved in a varus/valgus,posterior/anterior, and/or other direction.

The electronic control unit 1102 can be configured to receive theinformation from this additional sensor or sensors 40, and/or thesensor's communications device, and combine that information withinformation from the sensor or sensors 40 located within the surgicalorientation device 12 to calculate an overall, or aggregate, movementand orientation of the surgical orientation device 12 relative to anaxial line or plane. The electronic control unit 1102 can correct forchanges in position of this axis or plane, and the display 24 canindicate to the user an appropriate varus/valgus and/orflexion/extension angle for resection, based on the actual location ofthe mechanical axis or plane.

Additionally, this additional sensor or sensors 40 can be located in adevice. The device can be constructed such that the device isautoclavable and reusable, and can allow insertion and removal of adisposable battery. The additional sensor or sensors 40 can beincorporated with any of the systems and/or methods described herein,and can be placed on any of the components of the systems describedherein.

B. Acquiring Orientation Information Using a Visible Indicator andTarget Probes

1. Pre-Operative Planning

Pre-operative planning can be used to prepare for a joint replacementprocedure. For example, in a knee replacement procedure, the user canassess a desired varus/valgus angle and flexion/extension angle forresection of the tibia along a proximal portion of the tibia. Thisassessment can be made, for example, by clinical inspection (e.g. x-raysor manual visual inspection) of the knee prior to surgery. Thepre-operative planning will usually determine what angle or angles ofresection will be appropriate prior to attachment of the prosthetic kneecomponent or components to the tibia.

The leg can then be secured by placement in a leg holder, and the kneecan be exposed using a standard surgical procedure. Osteophytes on theproximal tibia can be removed, and a resection depth of the tibia can bedetermined by using a stylus or other instrumentation. For example,depth of resection can be determined by aligning the stylus length-wise,parallel with the tibia, with the depth of resection being determined bythe point of contact between the tip of the stylus and the lowest pointof a medial condyle of the proximal tibia. This resection depth canprovide an indication to the user of what size prosthetic component orcomponents to use, as well as how far to cut into the tibia with acutting tool (e.g. saw blade).

2. Registering the Coronal and Sagittal Planes

After pre-operative planning for a joint replacement procedure, thetibial preparation system 10 described above can be used to identify thelocation and orientation of an axial line, as well as to orient acutting block relative to the axial line.

For example, once the desired varus/valgus and posterior/anterior anglesfor resection have been determined pre-operatively, the tibialpreparation system 10 can be assembled. The surgical orientation device12, coupling mechanism 14, and universal jig 16 can be coupled together,and the tibial preparation system 10 can be positioned adjacent theproximal tibia on an anterior side of the tibia (i.e. front of the leg).

In a preferred arrangement, the tibial preparation system 10 can bepositioned and/or moved until the surgical orientation device 12 isgenerally centered with the insertion of an anterior cruciate ligamentand a medial tibial insertion of the patella tendon in a patient's knee.To achieve this centering, the surgical orientation device 12 can emit alaser beam or beams proximally from one of its optical components 32.This laser beam or beams can illuminate a portion of the knee joint, andthe tibial preparation system 10 can be moved until the laser beam isaligned with at least one of the insertion of the anterior cruciateligament and the medial tibial insertion of the patella tendon (e.g. themedial third of the tibial tuberosity). For example, if the opticalcomponent 32 emits a cross-hair beam, centering can be verified with avertical portion (e.g. one which is parallel to or coincident with asagittal plane extending through the leg) of the beam being aligned withboth the insertion of the anterior cruciate ligament and the medialtibial insertion of the patella tendon.

With reference to FIG. 21 a, once centering has been achieved, the basemember 78 of the universal jig 16 can be coupled to or otherwise securedadjacent to a proximal portion of the tibia T. Preferably, the couplingsecurement is such that the base member 78 has zero or substantiallyzero degrees of freedom relative to the tibia T. In one technique, thebase member 78 is pinned, which comprises placing at least one pin orother anchoring device through the holes 102 a described above and intoan anterior face of the tibia.

The user can then pick up and adjust locations of the target portions108 of the target probes 18 a, 18 b. For example, the lengths of thetarget probes 18 a, 18 b can be adjusted to take into account adistance, which exists after attachment of the universal jig 16 to thetibia, between the optical element 32 of the surgical orientation device12 and a mechanical axis of the leg.

In a preferred arrangement, a stylus, marker pin, or other measuringdevice can be used to measure the distance between an A/P point on theproximal tibia and a plane parallel to a coronal plane containing themechanical axis. This distance can be measured, for example, byreferring to analogous numbering systems labeled on both the targetprobe 18 a, 18 b and the measuring device. For example, a FIG. 21 bshows a tibial preparation system 10′. The tibial preparation system 10′is similar to the preparation system 10 described above, and includesthe surgical orientation device 12 and a universal jig 16′. Themeasuring device 109, as shown in FIG. 21A, can be located proximal thecutting block 84 in a system 10 or 10′. The measuring device 109 a cancomprise etchings, or markings, to measure distance. The measuringdevice 109 a can be moved, for example, until a tip 109 b of themeasuring device 109 a is resting over the insertion point of theanterior cruciate ligament in the knee (for example as shown in FIG.21B), and/or a soft point on the top of the tibia commonly referred toas the A/P point of the mechanical axis. This point is located along atibial spine on top of the tibia, and generally marks the location of apoint along the mechanical axis of the leg.

The user can use the measuring device 109 a to measure the distancebetween the coronal plane containing the mechanical axis (including theA/P point) and, for example, the location of the optical element 32 onthe surgical orientation device 12. Once this distance is known, thelength of the target probes 18 a, 18 b can be adjusted until the targetportions 108 are approximately the same distance anterior of a coronalplane containing the mechanical axis as is optical element 32 on thesurgical orientation device 12.

In another embodiment, the distance between the optical element 32 ofthe surgical orientation device 12 and the coronal plane containing themechanical axis can be measured directly with the target probe 18 a, 18b itself (for example, using a target probe 18 a, 18 b that contains anadjustable marker), such that a desired length of the target portion 108on the target probe 18 a, 18 b can be set directly.

Once the length of the target probe 18 a, 18 b is set, the user canpalpate adjacent to a distal feature of the patient's tibia, such as forexample the ankle, to find a location of the lateral malleolus. Oncethis location is found, the user can hold, couple, and/or affix a firsttarget probe 18 a adjacent to a distal feature of the patient's tibia,such as for example onto the lateral malleolus as shown in FIG. 21B.

The laser 42 can then be activated. FIG. 21 b shows the tibialpreparation system 10′ with its laser 42 turned on. For example, anoptical element 32 on the surgical orientation device 12 can beactivated by pressing one of the user inputs 26 on the surgicalorientation device 12, and can emit a crosshair laser beam distallytoward the ankle, and toward the first target probe 18 a.

With at least one cross-hair laser beam pointing towards the ankle, theknobs on the universal jig 16 can be adjusted until the laser beamilluminates a target shape 110 on the target portion 108 of target probe18 a. As described above, the target shape 110 can be a cross-shapedobject, slot, cross mark, T-shaped, L-shaped, or some other shapecontaining perpendicular lines that meet or intersect. The user canadjust the position of the universal jig 16 until the crosshair beam ofthe laser beam lines up in both directions along or through the targetshape 110.

In some embodiments, the target probe 18 a, 18 b can contain a sensor todetect feedback from the cross-hair beam of the laser and can beconfigured to emit noise or other feedback to confirm that thecross-hair beam of the laser has been positioned correctly on the targetportion 108 of target probe 18 a, 19 b.

Once the cross-hair beam of the laser is aligned with the target shape110, the user can input the orientation of the surgical orientationdevice 12 (and simultaneously cutting block 84), into the surgicalorientation device 12 as a first reference position. For example, theuser can press one of the user inputs 26 on the surgical orientationdevice 12, and the surgical orientation device 12 can register and/orcalculate the current orientation of the surgical orientation device 12based on data collected from the sensor or sensors 40. The orientationof the surgical orientation device 12 in this first reference positioncan be used to identify the orientation of a coronal plane that containsthe mechanical axis of the leg. In one technique, data collected fromthe sensor 40 in connection with the probe 18 a can also be used todetermine a first reference point for identifying the location and/ororientation of a sagittal plane containing the same mechanical axis.

The user can then position a second target probe or probes 18 b on themedial malleolus, the location of which may be determined by againpalpating the ankle. Once the location of the medial malleolus isidentified and the second target probe or probes 18 b are held in place,the universal jig 16 can be adjusted until a beam of the cross-hairlaser beam illuminates a desired target shape 110 on a second targetprobe 18.

Once the second target probe 18 b has been positioned properly, thesurgeon can again press one of the user inputs 26 on the surgicalorientation device 12, and the surgical orientation device 12 canregister and/or calculate the current orientation of the surgicalorientation device 12 in the second reference position based on datacollected from the sensor or sensors 40 inside the surgical orientationdevice 12. The orientation of the surgical orientation device 12 in thissecond reference position can be used to identify the orientation of aplane extending through the tibia which contains the mechanical axis ofthe leg, and/or can be used to locate a second reference point foridentifying the location and/or orientation of a sagittal planecontaining the mechanical axis.

When using the surgical orientation device 12 to determine the first andsecond reference positions, output of the sensors 40 in the surgicalorientation device 12 can be monitored after light is directed to theselected location in a manner that minimizes error in the reading. Forexample, a transient phase can be eliminated in the output of thesensors 40 to arrive at an accurate estimation of the given anatomicallandmark and/or target probe 18. The electronic control unit 1102 can beconfigured to perform stabilization algorithms or methods to minimize orsubstantially remove erroneous output caused by vibrational or othermovements, as described above.

With continued reference to FIGS. 21 a and 21 b, once information aboutboth the first and second reference positions has been acquired andregistered in the surgical orientation device 12, the user can directthe surgical orientation device 12 to calculate the location of adesired point between the lateral malleolus and the medial malleolus.This desired point can lie within the aforementioned sagittal planecontaining the mechanical axis. The desired point can vary, depending onthe user's medical training and experience. For example, the desiredpoint can be located midway between the lateral malleolus and medialmalleolus, or 55% toward the medial malleolus from the lateralmalleolus, or at some other predetermined location.

The user can use one or more user inputs 26 to provide commands todirect the surgical orientation device 12 to calculate the location ofthis desired point and to calculate the location and/or orientation ofthe sagittal plane containing this desired point. Once the surgicalorientation device 12 has calculated where this desired point is, thesurgical orientation device 12 can provide location feedback to theuser, for example in the form of a visual signal or signals on thedisplay 24, indicating that the location of this desired point, and/orthe location of the sagittal plane, has been calculated.

In some embodiments, two target probes 18 a can be used, each with across target 110. One of the target probes 18 a can first be used toidentify a coronal plane containing the mechanical axis, and both thetarget probes 18 a can then be used to identify a sagittal planecontaining the mechanical axis. Since the coronal plane can beregistered by the first target probe 18 a with a cross target 110, theuser can line up a vertical portion of the cross-hair laser beam (e.g.one which is parallel or coincident with a sagittal plane extendingthrough the leg) with the vertical portion of the second target probe 18a, and the location of the sagittal plane can be calculated. Thisalignment can be made without lining up both the horizontal and verticalportions of the cross-hair laser beam on the second target probe 18 a,since doing so can cause the orientation of the surgical orientationdevice 12 to deviate from the already registered coronal plane.

3. Adjusting an Orthopedic Fixture to Set a Cutting Block Orientation

Once the location of the coronal and sagittal planes containing themechanical axis has been acquired and registered by the surgicalorientation device 12, the surgical orientation device 12 can calculateand store the location and orientation of the mechanical axis of theleg. Based on this stored information, the surgical orientation device12 can be used to adjust the cutting block 84 in order to obtain adesired orientation for resection of the proximal tibia. For example,the universal jig 16, 16′ can be adjusted to move the surgicalorientation device 12.

With reference to FIG. 2, both a varus/valgus angle andposterior/anterior angle of the cutting block 84 can be set by the user.In order to adjust these angles of the cutting block 84, the user canturn the knobs 90 a, 96 a on the ends of pins 90 and 96 on the universaljig 16. Turning these knobs can change the angle and/or orientation ofthe varus/valgus adjustment block 82, and posterior/anterior adjustmentblock 80, respectively. As the varus/valgus adjustment block 82 andposterior/anterior adjustment block 80 are moved (e.g. rotated), thecutting block 84 can also be moved, along with the surgical orientationdevice 12.

As the cutting block 84 is moved (e.g. swung) in a varus/valgusdirection, the surgical orientation device 12 can provide a reading orreadings on its display 24 indicating whether the surgical orientationdevice (and likewise the cutting block 84) is aligned with the sagittalplane containing the mechanical axis, or whether the cutting block 84 isangled at some degree relative to the sagittal plane containing themechanical axis. For example, the surgical orientation device 12 canindicate on its display 24 a difference in degrees between the currentorientation of the cutting block 84, and an orientation of the cuttingblock 84 in which the cutting block 84 is aligned substantially orexactly parallel to (or exactly on) the sagittal plane containing themechanical axis.

Similarly, as the cutting block is moved (e.g. swung) in aposterior/anterior direction, the surgical orientation device 12 canprovide a reading or readings on its display 24 indicating whether thesurgical orientation device (and likewise the cutting block 84) isaligned with the coronal plane containing the mechanical axis, orwhether the cutting block 84 is angled at some degree relative to thecoronal plane containing the mechanical axis. For example, the surgicalorientation device 12 can indicate on its display 24 a difference indegrees between the current orientation of the cutting block 84, and anorientation of the cutting block 84 in which the cutting block 84 isaligned substantially or exactly parallel to the coronal planecontaining the mechanical axis.

In some embodiments, the cutting block 84, or other cutting blocksdescribed herein, can be attached to a universal jig after the universaljig has been adjusted. Thus, the final position of the cutting block canbe adjusted, and the cutting block can then be attached, as opposed tobeing attached during the entire adjustment process.

The surgical orientation device 12 can further be useful in settingand/or confirming a resection depth of the tibia once the varus/valgusand posterior/anterior angles have been determined. For example, in apreferred arrangement, the user can activate the laser 42 (e.g. aproximal cross-hair beam laser) on the surgical orientation device 12 bypressing one of the user inputs 26, and can hold or attach a device forconfirming a cut line or plane, for example a mirror 226 as shown inFIG. 22A of the system 210. The mirror 226 can be coupled to orintegrally formed with the universal jig 16 or other surgical component.The mirror 226 can be held or attached at a certain angle such that ahorizontal beam of the cross-hair beam, extending, for example, parallelto a coronal plane, is reflected through an opening 102 on the cuttingblock 84 and onto the tibia, illuminating an area on the tibia which acutting saw would cut through if moved through the cutting block 84. Thepoints of bone on the tibia which prevent the passage of the laser beam(and which are therefore illuminated by the laser) across the tibia arethose which would be resected by the cutting saw. In the event that adifferent depth of the resection is desired, the user can adjust thecutting block 84 and reconfirm depth of resection.

C. Tibial Preparation System with Mechanical Referencing of a DistalLandmark

A tibia preparation system can be provided which uses a moveableorthopedic fixture with a probe to reference one or more anatomicallandmarks mechanically. The probe can comprise a mechanical swing arm.For example, FIGS. 2 b and 22-23 illustrate a tibial preparation system210. Tibial preparation system 210 is a variation on the tibialpreparation system 10 described above, and can comprise the surgicalorientation device 12 described above, as well as a universal jig 212.The tibial preparation system 210 can differ from the tibial preparationsystem 10, for example, in that the system 210 can utilize a mechanicalstructure or structures to locate anatomical landmarks adjacent thedistal tibia, as opposed to using a target or targets with a lightsource as described above.

1. Orthopedic Fixture for Orienting a Surgical Orientation Device and/orCutting Block in Multiple Degrees of Freedom

An orthopedic fixture can be provided for orienting a surgicalorientation device and/or cutting block. For example, the universal jig212 can be similar to the universal jig 16 described above. Withreference to FIGS. 22A-C, the universal jig 212 can comprise a basemember 214 operatively coupled to a posterior/anterior adjustment block216, and/or a varus/valgus adjustment block 218.

a. Base Member for Providing an Anchored or Fixed Initial Position of anOrthopedic Fixture

A base member can be provided which anchors an orthopedic fixture and/orprovides a fixed initial position of a moveable orthopedic fixture. Forexample, the base member 214 can comprise a structure which is rigidlyand/or fixedly attached to an anatomical structure, such as a bone. In apreferred arrangement, the base member 214 can comprise a proximalmounting structure, such as for example at least two base memberattachment openings (not shown) which are in the form of holes extendingthrough the base member 214. Each of the base member attachment openingscan be configured to receive a fastening device, such as for example ascrew, to anchor the base member 214 into a bone or other anatomicalstructure and fix the base member 214 relative to the bone or anatomicalstructure. For example, the base member 214 can be mounted on a proximalportion of the tibia.

The base member 214 can further comprise an elongate base member rod220, similar to rod 92 described above. The elongate base member rod 220can extend distally from an upper, or proximal, portion of the basemember 214, and can include a brace-like structure 222 on its distalend, similar to structure 94 described above. The brace-like structure222 can be curved to better conform to the curvature of the anatomy. Thebrace-like structure 222 can be used to brace and/or hold the universaljig 212 against the patient's skin overlying the tibia during the kneereplacement procedure. For example, and as described above, thebrace-like structure 222 can provide a stabilizing force.

Similar to the system 10, the base member 214 can be operativelyconnected to a cutting block 224, as described further herein. Thecutting block 224 can be located proximal the base member 214, and canmove relative to the base member 214.

The base member 214 can further comprise a device for confirming a cutline or plane, as described above. For example, the base member cancomprise a mirror 226. The mirror 226 can be formed as part of thecutting block 224, or other surgical component. The mirror 226 cancomprise a 45 degree (or other angle) reflective surface, which canreflect a light beam or beams along the surface of an anatomicalfeature. For example, and as described above, the mirror 226 can beangled and/or fixed such that a beam of a cross-hair laser beam isreflected through an opening 102 on the cutting block 224 and onto thetibia, illuminating an area on the tibia which a cutting saw would cutthrough if moved through the cutting block 224.

b. Device for Adjusting a Posterior/Anterior Slope of a Cutting Block

An adjustment device can be provided which can be used to adjust theorientation of a surgical orientation device and/or cutting block. Forexample, and with continued reference to FIGS. 22 and 23, aposterior/anterior adjustment block 216 can comprise a structure that ismoveable (e.g. rotatable) in at least one of a posterior and anteriordirection. For example, the universal jig 212 can include at least oneknob 228. When the knob 228 is turned, the posterior/anterior adjustmentblock 216 can rotate about a hinge, pin, or other structure, such as forexample pin 229, in the universal jig 212 to change a posterior/anteriorangle of the cutting block 224. As discussed further below, the surgicalorientation device 12 can be coupled to the adjustment block 216 formovement therewith. Thus, movement of the adjustment block 216 can alsochange the plane angle of the surgical orientation device 12.

The posterior/anterior adjustment block 216 can further comprise aconnector 230. The connector 230 can comprise a structure whichoperatively connects the posterior/anterior adjustment block 216 to thesurgical orientation device 12. For example, the connector 230 cancomprise a structure which facilitates translational movement of thesurgical orientation device 12 relative to the posterior/anterioradjustment block 216. The connector 230 can comprise a channel 231. Thechannel 231 can facilitate movement of an upper, or proximal, portion232 of the posterior/anterior adjustment block 216 relative to theconnector 230 (e.g. sliding movement).

With reference to FIGS. 22 b and 23, the connector 230 can comprise, orbe attached to, a clamp 233. The clamp 233 is a coupling device similarto the coupling device 14 described above. For example, the clamp 233can be secured to the back side of the surgical orientation device 12 tocouple the surgical orientation device 12 to another structure orstructures. In the tibia preparation system 210, the clamp 233 can beused to couple the surgical orientation device 12 to theposterior/anterior adjustment block 216.

With reference to FIGS. 22-23, the connector 230 can further comprise,or be attached to, a swing arm 234. The swing arm 234 can comprise alandmark acquisition device which can be used to locate and/or identifyspecific landmarks, such as for example landmarks adjacent the distaltibia. The swing arm 234 can comprise an elongated structure orstructures, such as for example a metal rod or rods, which can extendfrom a proximal portion of the tibia (e.g. near the knee joint) to adistal portion of the tibia (near the ankle). The swing arm 234 canextend generally vertically (e.g. in a proximal to distal direction)behind the surgical orientation device 12, and/or can be hinged, suchthat at least one of a distal portion 236 and proximal portion 238 ofthe swing arm 234 can swing and/or rotate relative to the other proximalor distal portion 236, 238. For example, the distal and proximalportions 236, 238 can comprise elongate structures connected by a hingeportion 239 located between the distal and proximal portions 236, 238.The hinge portion 239 can permits relative movement of the distalportion 236 with respect to the proximal portion 238. In otherembodiments the swing arm can comprise more than one hinge portion 239.The hinge portion or portions 239 can be located at other locations thanthat shown in FIGS. 22 a, 22 b, and 23. The swing arm 234 can alsocomprise a distal end 240. The distal end or tip 240 can comprise apointed structure or structures, and/or a distal mounting structure,which can contact and/or couple with an anatomical landmark. Forexample, the hinge portion 239 of the swing arm 234 can be moved orswung until the tip 40 is in contact with, or is coupled to, ananatomical landmark adjacent the distal tibia.

Similar to the universal jig 16 described above, the posterior/anterioradjustment block 216 of universal jig 210 can be operatively connectedto the cutting block 224. Movement of the posterior/anterior adjustmentblock 216 and cutting block 224 can be linked (e.g. by pins, hinges,etc.) such that movement of the posterior/anterior adjustment block 216can cause similar or identical movement of the cutting block 224.Movement of the cutting block 224 can, at the same time, cause similaror identical movement of the surgical orientation device 12.

While the swing arm 234 is described as forming part of theposterior/anterior adjustment block 216, the swing arm 234 canalternatively be formed as part of the base member 214 and/orvarus/valgus adjustment block 218 described below. Similarly, while thebase member 214 is described as being separate from theposterior/anterior adjustment block and varus/valgus adjustment block218, the base member can, in at least some embodiments, refer generallyto a combination or combinations of the posterior/anterior adjustmentblock 216, swing arm 234, and/or varus/valgus adjustment block 218.

c. Device for Adjusting a Varus/Valgus Slope of a Cutting Block

An adjustment device can be provided which can be used to adjust theorientation of a surgical orientation device and/or cutting block. Forexample, and with continued reference to FIGS. 22A-C, the varus/valgusadjustment block 218 can comprise a structure which is moveable (e.g.rotatable) in at least one of a varus/valgus direction. For example, theuniversal jig 212 can include at least one knob 242. When the knob 242is turned, the varus/valgus adjustment block 218 can rotate about ahinge, pin, or other structure in the universal jig 212 to change avarus/valgus angle of the surgical orientation device 12, as well as thecutting block 224.

Movement of the varus/valgus adjustment block 218 can correspond to orresult in movement of the posterior/anterior adjustment block 216. Forexample, a portion or portions of the varus/valgus adjustment block 218can rest within and/or be contacted on either side by portions of theposterior/anterior adjustment block 216, such that any movement of thevarus/valgus adjustment block 218 in a varus or valgus directionlikewise causes similar or identical varus/valgus movement of theposterior/anterior adjustment block 216.

d. Cutting Block which can be Oriented in a Posterior/Anterior, and/or aVarus/Valgus, Direction for Bone Resection

A cutting block, or other orthopedic fixture, can be provided for boneresection. The cutting block can be oriented with the aid of a surgicalorientation device, an orthopedic fixture, or a surgical orientationdevice and an orthopedic fixture. The cutting block 224, as describedabove, can comprise at least one opening 102. For example, one opening102 can comprise an elongate slit along a width of an upper, orproximal, portion of the cutting block 224 for receiving and guiding asaw, blade, or other cutting tool. Other openings 102 a (not shown) cancomprise holes for insertion of an anchoring pin or pins, or otherstructures.

2. Modified Orthopedic Fixture

The system 210 described above can be modified. For example, FIGS. 23Aand 23B show a system 210′. The system 210′ is a modification of system210, and can comprise a universal jig 212′ similar to the jig 212described above. The system 210′ can also comprise a surgicalorientation device 12. The universal jig 212′ can be adjusted by moving(e.g. pivoting) a swing arm 234′ by hand about a proximal portion 212 aof the universal jig 212′, rather than adjusting knobs by hand. Theproximal portion 212 a can comprise a varus/valgus adjustment device(such as the one described above), a posterior/anterior adjustmentdevice (such as the one described above), and/or a pivot pin or pins.Knobs can be included for locking the swing arm 234′ in place. In someembodiments the universal jig 210′ can comprise knobs for fine-tuneadjusting. In one embodiment, the swing arm 234′ can comprise anextendable portion that enables a distal portion thereof to be extendedaway from a base portion. The distal portion can include a moveable rodextendable from another member (e.g., a hollow rod) that is fixed to thebase. The distal portion can be fastened in any of a range of positionsrelative to the fixed, proximal portion. The distal portion preferablycan be clamped in a range of positions. In one embodiment a distalportion of the swim arm 234′ can be coupled with a block to enableadjustment of a tip into contact with anatomical landmarks. In someembodiments, the jig 212′ can be coupled with a proximal tibia and thearm 234′ is adapted to contact lateral or medial malleolus. In someembodiments, the jig 212′ can be coupled with a distal femur and the arm234′ is adapted to contact a structure corresponding to a femoral head,a lesser trochanter or a greater trochanter, as discussed herein.

With reference to FIG. 23A, the modified system 210′ can comprise ameasuring device 109 a, and a measuring device 109 c. As described abovewith respect to system 10, the measuring device 109 a can be used tomeasure a distance between an A/P point along the top of the tibia and acoronal plane parallel to the coronal plane containing the mechanicalaxis. The measuring device 109 a can include a marking or markingsproviding a visual indication of distance, and can slide within a block109 d. The measuring device 109 c can also measure a distance, and caninclude a marking or markings to provide a visual indication ofdistance.

D. Acquiring Orientation Information Using Mechanical Referencing of aDistal Landmark

1. Registering the Coronal and Sagittal Planes

After pre-operative planning for a joint replacement procedure, thetibial preparation system 210, 210′ described above can be used toidentify the location and orientation of an axial line, as well as toorient a cutting block relative to the axial line.

For example, once the desired varus/valgus and posterior/anterior anglesfor resection have been determined pre-operatively for a kneereplacement procedure as describe above, the tibial preparation system210, 210′ can be provided. In one technique at least some of thecomponents are modular, enabling using such component with multipleother orthopedic components. As such, the tibial preparation system 210,210′ can be assembled from these components.

The surgical orientation device 12 can be coupled to the universal jig212, and the tibial preparation system 210, 210′ can be positionedadjacent the proximal tibia on an anterior side of the tibia (i.e. frontof the leg). In other techniques, the tibial preparation system 210,210′ is partially or completely pre-assembled or integrated.

In a preferred arrangement, the tibial preparation system 210, 210′ canbe positioned such that the surgical orientation device 12 is generallycentered with the insertion of an anterior cruciate ligament and amedial tibial insertion of the patella tendon in a patient's knee, forexample as described above with respect to tibial preparation system 10.Once centering has been achieved, the base member 214 of the universaljig 212, 212′ can be pinned, anchored, and/or otherwise secured to thetibia, such that the base member 214 has zero or substantially zerodegrees of freedom relative to the tibia.

The user can then slide the connector 230 in a posterior and/or anteriordirection (e.g. translate the connector 230 forwards or backwards),until the swing arm 234, 234′ is located proximate an anatomicallandmark. For example, the connector 230 can slide until the tip 240 ofthe swing arm 234, 234′ is located adjacent the lateral malleolus on thepatient's ankle. The lower, or distal, portion 238 can swing and/orrotate during such movement in order to get the tip 240 closer to thelateral malleolus.

In a preferred arrangement, measuring devices 109 a and 109 c, such asthe ones illustrated in system 210′, can be used. For example, onemeasuring device 109 a can be located proximal the universal jig 212 or212′, and another measuring device 109 c can be located at a distal endof the swing arm 234 or 234′.

The measuring devices 109 a can be moved until a tip of the measuringdevice 109 a is resting over the insertion point of the anteriorcruciate ligament in the knee, and/or a soft point on the top of thetibia commonly referred to as the A/P point of the mechanical axis. Asdescribed above, this point is located along a tibial spine on top ofthe tibia, and generally marks the location of a point along themechanical axis of the leg.

The measuring device 109 c can then be moved until a tip 240 or 240′ ispositioned next to the lateral malleolus (for example as shown in FIG.23B). For example, the user can palpate adjacent to a distal feature ofthe patient's tibia, such as for example the ankle, to find a locationof the lateral malleolus of the tibia. Once this location is found, theuser can position the tip 240, 240′ of the swing arm 234, 234′ adjacentto a distal feature of the patient's tibia, such as onto the lateralmalleolus as shown in FIG. 23B.

The measuring devices 109 a, 109 c can then be adjusted until portions109 d are approximately the same distance anterior of a coronal planecontaining the mechanical axis, placing the surgical orientation device12 in an orientation parallel to that of the coronal plane containingthe mechanical axis. Each measuring device 109 a, 109 c can haveanalogous numbering systems. For example, the measuring devices 109 a,109 c can comprise etchings, or markings.

The user can activate the surgical orientation device 12, such as bypressing one of the user inputs 26 on the surgical orientation device12. Once activated, the, surgical orientation device 12 can register(e.g. record) the orientation of the surgical orientation device as afirst reference position. For example, the surgical orientation device12 can register and/or calculate the current orientation of the surgicalorientation device 12 based on data collected from the sensors 40. Theorientation of the surgical orientation device 12 in this firstreference position can be used to identify and register the orientationof a coronal plane which contains the mechanical axis of the leg, aswell as to determine a first reference point for identifying thelocation and/or orientation of a sagittal plane containing this samemechanical axis.

The user can then swing the swing arm 234, 234′ over to the other (e.g.medial) side of the leg, such that the tip 240, 240′ is located adjacentthe medial malleolus. For example, the user can turn the knob 242 onsystem 210 so that the posterior/anterior adjustment block 216,connector 230, and swing arm 234 are moved in a varus/valgus manner,until the swing arm 234 has moved to the other side of the leg. Thelower, or distal, portion 238 of the swing arm 234 can swing and/orrotate during such movement in order to avoid hitting or contacting thean anterior side of the leg.

The user can then again palpate the ankle, and position the tip 240,240′ of the swing arm adjacent to the medial malleolus. Once thelocation of the medial malleolus is identified, the user can press oneof the user inputs 26 on the surgical orientation device 12 to cause thesurgical orientation device 12 to determine the orientation of thesurgical orientation device 12 in a second reference position. Forexample, the surgical orientation device 12 can register and/orcalculate the current orientation of the surgical orientation device 12based on data collected from the sensors 40.

The orientation of the surgical orientation device 12 in this secondreference position can be again be used to identify the orientation of acoronal plane extending through the tibia that contains the mechanicalaxis of the leg, and/or can be used to locate a second reference pointfor identifying the location and/or orientation of a sagittal planecontaining the same mechanical axis.

When using the surgical orientation device 12 to determine the first andsecond reference positions, output of the sensors 40 in the surgicalorientation device 12 can be monitored in a manner that minimizes errorin the reading. For example, a transient phase can be eliminated in theoutput of the sensors 40 to arrive at an accurate estimation of thegiven anatomical landmark as discussed above.

Once information about both the first and second reference positions hasbeen acquired and registered in the surgical orientation device 12, thesurgical orientation device 12 can determine (e.g. calculate) thelocation of a desired plane between the lateral malleolus and the medialmalleolus. As described above, the desired plane corresponds to thesagittal plane containing the mechanical axis. The desired plane canvary, depending on factors such as the patient's specific anatomy andthe surgeon's training and experience. For example, the desired planecan be located midway between the lateral malleolus and medialmalleolus, or 55% toward the medial malleolus from the lateralmalleolus, or at some other predetermined location.

The user can use one or more user inputs 26 to direct the surgicalorientation device 12 to calculate the location of and/or orientation ofthe sagittal plane. Once the surgical orientation device 12 hascalculated where the sagittal plane is, the surgical orientation device12 can provide location feedback to the user, for example in the form ofa visual signal or signals on the display 24, indicating that thelocation of the sagittal plane has been calculated.

2. Adjusting an Orthopedic Fixture to Set the Orientation of a CuttingBlock

Once the locations of the coronal and sagittal planes containing themechanical axis have been acquired (e.g. registered) by the surgicalorientation device 12, the surgical orientation device 12 can calculateand store the location and orientation of the mechanical axis of theleg. Based on this stored information, the surgical orientation device12, and universal jig 212, 212′, can be used to adjust a cutting blockin order to obtain a desired orientation for resection of the top of thetibia.

For example, and as described above with respect to tibial preparationsystem 10, the knob or knobs 90 a, 96 a on the universal jig 212 can beturned to set a desired varus/valgus and posterior/anterior angle forresection. During this adjustment, the surgical orientation device 12can provide a reading or readings on its display 24 indicating whetherthe surgical orientation device (and likewise the cutting block 224) isaligned with the sagittal plane and/or coronal plane containing themechanical axis, or whether the cutting block 224 is at an acute anglerelative to the sagittal plane and/or coronal plane containing themechanical axis.

Once the orientation of the cutting block 224 has been adjusted and set,the mirror 226 can be used. For example, the user can press one of theuser inputs 26 on the surgical orientation device 12 to direct a laserbeam out of the optical element 32 and onto the mirror 226. The laserbeam can be reflected through an opening 102 on the cutting block 224and onto the tibia, illuminating an area on the tibia for resectionthrough the cutting block 224. The points of bone on the tibiailluminated by the laser are those which would be resected by thecutting saw. In the event that a different depth of the resection isdesired, the user can adjust the cutting block 224 and reconfirm depthof resection.

E. Other Target Systems and Methods

While the tibial preparation systems 10, 10′, 210, and 210′ and theirmethods of use are described above specifically in terms of a systemthat incorporates a surgical orientation device 12, a universal jig 16or 212, a laser system, and/or a set of target probes 18 or swing arm234, in other embodiments other components can be used to determineanatomical planes on the human body and/or facilitate alignment ofsurgical devices, systems, and/or anatomical parts.

For example, a light system other than a laser system can be attached toa surgical orientation device that is otherwise similar to the surgicalorientation device 12 described above. A user can position the surgicalorientation device until the light is illuminating a target, such as forexample an anatomical landmark, and the surgical orientation device canacquire this first position as a reference. The user can then positionthe device until the laser is illuminating another anatomical landmarkand the surgical orientation device can acquire this second position asa reference. Third, fourth, and/or additional reference positions canalso be obtained in the same technique.

The surgical orientation device can employ an algorithm that calculatessome appropriate point (e.g. a midpoint), as directed by the user,between the two anatomical landmarks that corresponds to the position ofa desired anatomical plane. The surgical orientation device can alsoprovide feedback to the user to position the surgical orientation devicein alignment with this plane. Alternatively, if a desired plane or axiscan be determined based on the position of one, two, three, or moreanatomical landmarks, a system can be used to make such determinationbased on a light-mapping of such landmark(s) and correspondingcalculations performed by a surgical orientation device.

In some embodiments, the surgical orientation device 12, or othersurgical orientation device, can be held at some distance from the bodyby the user. The surgical orientation device 12 can be used as aregistration guide. For example, the user can activate a light system onthe surgical orientation device that illuminates a line along the body,such as for example along the mechanical axis. Once the line is visiblyaligned along the mechanical axis, the surgical orientation device canpress a user input 24 and the surgical orientation device can registeran orientation of the surgical orientation device. This orientationinformation can later be used to align orthopedic fixtures or cuttingblocks.

In some embodiments, the target systems described herein, or othertarget systems, can be used to locate targets on the hip, femur, orother areas of the body, and to use such targets to acquire planes oraxes extending through the body. For example, the universal jig 16 canbe attached on the femur, and the system 10, including target probes 18a, 18 b described above, can be used to locate landmarks such as thegreater trochanter, center of the head of a femur, a point of entranceof a ligament, or other landmarks, and use these landmarks to referencean anatomical plane or planes. Similarly, the universal jig 212 can beattached on the femur, and the system 210, including swing arm 234′ canbe used to reference an anatomical plane or planes.

F. Tibial Preparation System with Landmark Acquisition Assembly andExtramedullary Alignment Guide

FIGS. 3 a and 3 b show a tibial preparation system 310 (shown asassemblies 310 a and 310 b) for use in a joint replacement procedure,such as for example a knee replacement procedure. The tibial preparationsystem 310 can comprise the surgical orientation device 12 describedabove, the coupling device 14 described above, a landmark acquisitionassembly 312, and an extramedullary alignment guide 314. The tibialpreparation system 10 can be different from the systems 10 and 210, forexample in that the system 310 can utilize both a structural alignmentguide and surgical orientation device alongside a lateral side of thetibia (e.g. held alongside the tibia) to locate a plane containing themechanical axis, and a second structural alignment guide (with surgicalorientation device) attached along the anterior side of the tibia.

1. Orthopedic Fixture for Acquiring Anatomical Planes or Axes

An orthopedic fixture can be provided which can be used to identify andacquire anatomical planes and/or axes. For example, FIG. 24 shows anembodiment of a landmark acquisition assembly 312. The landmarkacquisition assembly 312 can comprise an orthopedic fixture which can beused to identify the location of an axial line or plane. The landmarkacquisition assembly 312 can comprise a structure or structures forcontacting an anatomical landmark or landmarks in order to obtain analignment of an axis or plane extending through those anatomicallandmarks.

For example, in a preferred arrangement, the landmark acquisitionassembly 312 can comprise an elongate member, for example a primary rod316, with a proximal end 317 a and a distal end 317 b. The landmarkacquisition assembly 312 can further comprise a connecting element orelements 318, and secondary rod or rods 320. The secondary rod or rods320 can comprise transverse members coupled with each of the proximaland distal ends 317 a, 317 b of the primary rod 316. While theembodiment shown in FIG. 24 includes a single primary rod 316, twoconnecting elements 318, and four secondary rods 320, other embodimentscan include other numbers or configurations of primary rods, connectingelements, and/or secondary rods. In some embodiments, the connectingelement 3218 can be made integral with the primary rod 316 or asecondary rod 320.

The landmark acquisition assembly 312 can be arranged, for example, suchthat each connecting element 318 connects the primary rod 316 to atleast one secondary rod 320. The secondary rods 320 and primary rod 316can be at right angles to one another, as illustrated in FIG. 11, or canbe at angles other than right angles.

FIG. 25A shows a first portion 322 and a second portion 324 of across-section of the primary rod 316. The first portion 322 can begenerally rounded, while the second portion 324 can be generally flat.The second portion 324 can facilitate connection with other componentsor devices in the system 310. For example, the second portion 324 can beconfigured to inhibit a connected device from rotating about or pivotingabout the primary rod 316. The first and second portions 322, 324 can bearranged to permit only one orientation for the landmark acquisitionassembly 312. Other configurations and shapes for a first portion 322and second portion 324 besides those illustrated in FIG. 25 are alsopossible.

FIG. 25B shows ends 326 of the secondary rod 320 which can be narrowedand/or or pointed. The ends 326 can be used to contact portions of thehuman body in order to locate and/or pinpoint landmarks on the body,such landmarks including but not limited to the proximal tibia near theligamentous attachment of the collateral ligaments, and the malleolusprotruding out of the ankle region. Other shapes and configurations forthe ends 326 are also possible. The secondary rod 320 can furtherinclude ribs, protrusions, or other structures which can engage theconnecting element 318 and permit the secondary rod or rods 320 to beadjusted within the connecting element 318.

FIG. 26 shows an opening 328 in the connecting element 318 which canreceive the primary rod 316 and facilitate connection of the primary rod316 to another structure or structures. As illustrated in FIG. 26, theopening 328 can be shaped to receive the primary rod 316. The opening328 can include a rounded portion and a flat portion both configured toengagingly receive the first portion 322 and second portion 324 of theprimary rod 316.

The connecting element 318 can further include additional openingsshaped to receive, for example, the secondary rods 320 shown in FIG. 25.The secondary rods 320 can be threaded, and openings of the connectingelement 218 can include internal threads to receive the secondary rods320. In a preferred arrangement, the opening 328, or other openings inthe connecting element 318, can include notches, or grooves, whichprovide tactile feedback to a user when the primary rod 316 and/orsecondary rod or rods 320 are sliding through the openings. The opening328 or other openings in the connecting element 318 can extend entirelythrough the connecting element 318, thus allowing the primary rod 316and/or secondary rod or rods 320 to be inserted entirely through theconnecting element 318.

2. Orthopedic Fixture for Orienting a Surgical Orientation Device

An orthopedic fixture can be provided for orienting a surgicalorientation device and/or cutting block. For example, FIG. 27 shows anextramedullary alignment guide 314. The extramedullary alignment guide314 can comprise an orthopedic fixture which can be attached, at leastin part, to an anatomical location, and can extend outside and/or alongan appendage of the body. The extramedullary alignment guide can be usedto aid in orienting a surgical orientation device, such as for examplesurgical orientation device 12, and for locating an axial line or plane.

As illustrated in FIG. 27, the extramedullary alignment guide 314 cancomprise a distal mounting structure, such as for example a clampingportion 330, which can clamp onto a distal feature of a patient's leg ortibia, such as for example an ankle. The extramedullary alignment guide314 can further comprise an elongate, extended rod 332 which can extendoutside the body and generally parallel to the tibia. The clampingportion 330 can include a slide 334, which permits the extended rod 332to slide and/or swing in front of the leg and tibia. The slide 334 cancomprise an elongate recess or recesses along the clamping portion. Theextended rod 332 can include a portion which fits within these recesses,and slides back and forth.

The extramedullary alignment guide can further comprise, or be attachedto, a proximal mounting structure, such as for example a cutting block84. The cutting block 84 can be identical to the cutting block 84described above. For example, the cutting block 84 can comprise anopening 102 for insertion of a cutting tool (e.g. a cutting saw).

G. Acquiring Orientation Information Using a Landmark AcquisitionAssembly and Extramedullary Alignment Guide

After pre-operative planning for a joint replacement procedure, thetibial preparation system 310 described above can be used to identifythe location and orientation of an axial line, as well as to orient acutting block relative to the axial line.

For example, the leg to be operated on can be secured by placement in aleg holder, and the knee can be exposed using standard surgicalprocedure. During this time an extramedullary alignment guide, forexample the extramedullary alignment guide 314, can be held in positionadjacent the leg. A single spike on an end of the extramedullaryalignment guide can be placed in a proximal medial tibial spine, suchthat an end of the extramedullary alignment guide is in position overthe proximal medial tibial spine. Alternatively, a non-spiked rod can beused with an ankle clamp holding the guide in place.

Resection depth of the tibia can then be determined by, for example,using a stylus on the extramedullary alignment guide. For example, adepth of resection can be determined by aligning the stylus length-wise,parallel with the tibia, with the depth of resection being determined bythe point of contact between the tip of the stylus and the lowest pointof the medial condyle of the tibia.

Once the desired varus/valgus and posterior/anterior angles forresection have been determined pre-operatively for a knee replacementprocedure, and the resection depth has been determined, the tibialpreparation system (referring to system 310 a) can be assembled as shownin FIG. 3 a. For example, the surgical orientation device 12, couplingmechanism 14, and landmark acquisition assembly 312 can be coupledtogether, and the landmark acquisition assembly 312 can be positionedlaterally alongside the tibia and outside of the leg.

FIGS. 28 and 29 show the tibial preparation system 310 a locatedlaterally alongside the tibia. Specifically, FIGS. 28 and 29 show thetibial preparation system 10 being used to locate and reference anorientation of an axial line, in this case the mechanical axis extendingthrough the lower (e.g. distal) leg.

In order to reference the orientation of the mechanical axis, thesecondary rods 320 on the landmark acquisition assembly 312 can beadjusted such that their pointed ends 326 contact specified landmarks onthe body. These landmarks can be pre-marked on the lower leg prior to aknee joint replacement procedure. Location of the landmarks can beacquired, for example, prior to a resection of the proximal tibia, withthe tibia subluxed sufficiently to expose the tibial plateaus.

As shown in FIGS. 28 and 29, the tibia preparation system 310 a can beused to acquire the mechanical axis in a coronal plane (i.e. acquire theorientation of a coronal plane containing the mechanical axis). Forexample, the secondary rods 220 can be adjusted and positioned such thatone secondary rod 220 contacts the lateral collateral ligament of theproximal fibula head and another secondary rod 320 contacts the apex ofthe lateral malleolus. Once the secondary rods 320 have been adjusted,and are in contact with the aforementioned anatomical landmarks, theorientation of the mechanical axis can be obtained.

One of the user inputs 26 on the surgical orientation device 12 (e.g. amiddle button below the display 24) can be pushed to record and/orregister the orientation of the mechanical axis. The landmarkacquisition assembly 312 can then be moved slightly back and forth untilthe surgical orientation device 12 indicates that the surgicalorientation device 12 has acquired a plane containing the mechanicalaxis and verifies that the orientation has been recorded in the surgicalorientation device 12. This indication can include, for example, areading of zero on display 24, or some other signal. In a preferredarrangement, the display 24 can display a zero degrees reading and aflashing light (e.g. a green light), as shown in FIG. 29.

Once the surgical orientation device 12 has acquired an orientation ofthe mechanical axis, the surgical orientation device 12 and couplingdevice 14 can be removed from the landmark acquisition assembly 312, andthe tibia preparation system can be re-assembled into system 310 b suchthat the surgical orientation device 12 and coupling device 14 arecoupled with the extramedullary alignment guide 314.

FIG. 30 shows the tibia preparation system 310 b in an assembled state.In a preferred arrangement, the extramedullary alignment guide 214 canbe aligned with the front of the leg. The clamping portion 330 can beused to clamp and/or secure a lower, or distal, portion of theextramedullary alignment guide 314 to the patient's ankle.

The extramedullary alignment guide 314 can be moved (e.g. rotated) in afirst degree of rotation (e.g. roll) until the sensor or sensors 40 inthe surgical orientation device 12 observe that the surgical orientationdevice 12 is in a plane parallel to the coronal plane containing themechanical axis of the leg. Once the sensor or sensors 40 inside thesurgical orientation device 12 observe that the surgical orientationdevice 12 is in this orientation, the surgical orientation device 12 canprovide an indication to the user. For example, the surgical orientationdevice 12 can display zero degrees and a flashing light on the display24. In a preferred arrangement, a pictorial representation of a bubblecan be displayed that, for so long as the surgical orientation device 12remains aligned with gravitational zero within an allowable range, stayswithin the confines of two vertical lines, each on one side of thebubble. The two vertical lines marking the confines of the “level”orientation range can correspond to a relative angle or tilt of plus andminus three degrees or plus and minus one degree, for example. Inanother embodiment, the graphical display of a bubble can be combinedwith a secondary indication to cue the user as to the state ofalignment. For example, if the bubble moves beyond the lines, thebackground color of the screen behind the bubble can change from a firststate (e.g., a first color, such as green) to a second state (e.g., asecond color, such as amber) to indicate that the orientation is out ofthe acceptable range. Once the user has received this indication, theuser can press a user input 26 (e.g. a middle button below display 24),confirming and/or registering the orientation of the surgicalorientation device 12.

The extramedullary alignment guide 314 can then be moved (e.g. rotated)in a second degree of rotation (e.g. pitch) until the sensor or sensors40 observe that the surgical orientation device 12 is in a planeparallel to the coronal plane containing the mechanical axis of thepatient's leg. Once the sensor or sensors 40 inside the surgicalorientation device 12 observe that the surgical orientation device 12 isin this orientation, the surgical orientation device 12 can againprovide an indication to the user. For example, the surgical orientationdevice 12 can display zero degrees and a flashing green light on thedisplay 24, and/or a bubble as described above. FIG. 31 shows such aflashing light on a display 24. Once the user has observed this light orother indication, the user can press a user input 26 (e.g. a middlebutton below display 24), confirming and/or registering the orientationof the surgical orientation device 12.

In some embodiments, the surgical orientation device can provide anindication when the surgical orientation device 12 is aligned in bothdegrees of freedom at the same time, rather than providing an indicationeach time separately. The user can then press the user input 26 once,rather than twice, to confirm registration of the orientation of thesurgical orientation device 12.

In yet other embodiments, the surgical orientation device 12 can monitorand store the output of tilt meter sensors 40 in the surgicalorientation device 12, such that when the tilt meter sensors 40 havebeen steady for a certain period, the surgical orientation device 12 canrecord the output to confirm and/or register the orientation of thesurgical orientation device 12. In one technique, the surgicalorientation device 12 can average the data recorded over a period oftime (e.g. data recorded over the last second or several seconds priorto pressing a user input 26) and use the average as the acquired datafor the coronal plane. This process can be used in other instances ofthe procedures described herein, for example when the surgeon or othermedical personnel is directing the surgical orientation device 12 toacquire a plane or orientation of the surgical orientation device 12.This method can be advantageous in that it can reduce and/or eliminateinaccuracies caused by physical movement during a key-press (or otherforce imposed by the surgeon or other medical personnel onto thesurgical orientation device 12, electrical noise due to the current flowduring a key-press (or other user action), other vibrational movement,or electrical and physical (audio) noise. In certain embodiments, thesurgical orientation device 12 can be configured to identify the datacorresponding to the time a button is pressed and then use the mostrecent “good” data obtained before the button was pressed by the user(for example, before the fluctuations in the data occurred due to thebutton press).

After registering the orientation of the mechanical axis as describedabove, the resection depth can be verified with a stylus. FIG. 32 showsa stylus 336. The stylus 336 can be attached to the extramedullaryalignment guide 214. The stylus 336, or other surgical instrument, canbe used to confirm and/or select a desired depth of resection for thetibial cut. This resection depth can be specified, for example, in animplant manufacturer's technique guide, and can help determine what sizeprosthetic component or components to use for the replacement kneejoint.

The user can then orient the cutting block 84 into the pre-operativelydetermined varus/valgus and posterior/anterior angles for resection. Forexample, the extended rod 332 of the extramedullary alignment guide 214can be adjusted (e.g. swung) in the sagittal (i.e. flexion/extension)plane in order to move the cutting block 84 into the pre-operativelydetermined posterior/anterior angle. In one arrangement, a lower, ordistal, portion of the extended rod 332 can be moved and/or adjustedfurther away from or closer to the clamping portion 330. FIGS. 33A and33B illustrate movement of the extended rod 332 towards the clampingportion 330. By moving the distal, end of the extended rod 332 away fromor closer to the clamping portion 330 of the extramedullary alignmentguide 313, the posterior/anterior angle the cutting block 84 can bealtered.

The extramedullary alignment guide 314 can additionally includemarkings, for example, which give an indication of the angle created byadjustment of the extended rod 332. In a preferred arrangement, thesurgical orientation device 12 can also provide a read-out on itsdisplay 24 of the angle of orientation of the resection plane created bymoving the extended rod 332.

Once the extended rod 332 is positioned as desired, a first mounting pin333, or other anchoring device, can be inserted through the cuttingblock 84, for example as shown in FIGS. 34A and 34B. Once this firstmounting pin 333 is inserted, the cutting block 84 and extending rod 332can be restricted from movement in all but a varus/valgus plane alongthe front of the tibia.

The user can then locate the sagittal plane containing the mechanicalaxis through use of a laser guide or guides. For example, the user canpress one of the user inputs 26 (e.g. the middle button beneath thedisplay 24) on the surgical orientation device 12 to activate a lasersystem in the surgical orientation device 12. When the laser system isactivated, the optical elements 32 on the top and bottom of the surgicalorientation device 12 can emit red (or other color) laser beams out ofthe surgical orientation device 12. The laser beams can be in the formof lines, planes, cross-hairs, or other configurations.

Other locations for a laser system or systems can also be used. Forexample, the laser system can be attached to or integrated with theprimary rod 316, secondary rods 320, and/or adjacent the surgicalorientation device 12. In some embodiments, the laser system can be anentirely separate feature or device. In some embodiments, the lasersystem can be used for establishing the correct cutting angle duringresection of the tibia and/or femur by providing beams which illuminatethe epicondyles and/or a Whiteside's line to establish proper rotationalorientation of a femoral implant.

FIGS. 35 a and 35 b illustrate how a laser system can be used to alignthe cutting block 84 with the sagittal plane which contains themechanical axis. Once activated, the laser system in the surgicalorientation device 12 can project a red laser light against the lowerleg, with the laser light forming a line or lines along the exterior ofthe lower leg to provide visual cues as to alignment. For example, andas shown in FIGS. 35 a and 35 b, the laser light (dashed line in thefigures) can emanate down the leg and extended rod 332 from an opticalelement 32 on the surgical orientation device 12, and can illuminate alandmark or landmarks, such as for example an anatomical landmarkbetween the first and second toes on the patient's foot. Because onlyone pin or other anchoring device is inserted into the cutting block 84,the extended rod 332, surgical orientation device 12, and cutting block84 can swing about the inserted first pin in a varus/valgus plane untilthe laser light is pointing to the desired landmark on the foot. FIGS.35A and 35B illustrate an example of this movement.

Once the laser light has hit the desired landmark, the user can press auser input 26 on the surgical orientation device 12, and the surgicalorientation device 12 can register the orientation of the sagittalplane. The surgical orientation device 12 can then provide a display ofthe varus/valgus angle as the varus/valgus angle changes relative tothis recorded initial position. For example, the display 24 can indicatezero degrees when the cutting block is aligned with the sagittal plane,and can read other values when the cutting block is swung one way or theother relative to the initial position. This can allow the user tochange the varus/valgus angle until the varus/valgus angle of thecutting block is at its pre-operatively determined value.

Once this desired value is obtained, the user can insert a second pin orpins, or other anchoring device or devices, through the cutting block 84and into the tibia. FIGS. 36A and 36B illustrate a second mounting pininsertion. Once the second mounting pin 333 is inserted, the cuttingblock 84 can be fixed in place, or substantially fixed in place.

Once the cutting block is fixed, the rest of the extramedullaryalignment guide 313, as well as the surgical orientation device 12 andcoupling device 14, can be removed. FIG. 37 illustrates the cuttingblock 84 fixed to the tibia, with a cutting tool beginning to resect thetibia by moving a saw blade through the opening 102.

H. Tibial Preparation System with a Single Orthopedic Fixture

A tibial preparation system can be provided which uses a singleorthopedic fixture, instead of two orthopedic fixtures as describedabove. For example, FIGS. 4 a and 4 b show a tibial preparation system410 for use in a joint replacement procedure, such as for example a kneereplacement procedure. The tibial preparation system 410 can comprisethe surgical orientation device 12 described above, the coupling device14 described above, and a landmark acquisition assembly 412. The tibialpreparation system 410 can be different from the systems 10, 210, and310, for example in that the system 410 can utilize a single structuralalignment device with a surgical orientation device, the alignmentdevice being used along the lateral side of the tibia (e.g. heldalongside the leg), as well as along the anterior side of the tibia.

The landmark acquisition assembly 412 can be similar to the landmarkacquisition assembly 312 described above. For example, the landmarkacquisition assembly 412 can comprise a primary rod, connecting elementor elements, and secondary rod or rods.

The landmark acquisition assembly 412 can further include a handle 414.The handle 414 can attached to or integrally formed with a first portion416 of the landmark acquisition assembly 414. For example, the handle414 can be attached to or integrally formed with a primary rod, or otherextending structure, of the first portion 416 of the landmarkacquisition assembly 412.

The handle 414 can also be releasably coupled to a second portion 418 ofthe landmark acquisition assembly 412. For example, one end of thehandle 414 can be screwed onto, and/or latched onto, an end of thesecond portion 418, such that the second portion 418 of the landmarkacquisition assembly 412 can be removed from the first portion 416.

The surgical orientation device 12 can be coupled to the landmarkacquisition assembly 412. For example, the surgical orientation device12 can be coupled to the first portion 416 of the landmark acquisitionassembly 412 with the coupling device 14. As shown in FIG. 4 b, thesurgical orientation device 12 can comprise a laser system or systems42.

A cutting block 84 can also be attached to or integrally formed with thefirst portion 416, and can itself be attached to or integrally formedwith a stylus 420 used for determining resection depth.

I. Acquiring Orientation Information Using a Single Orthopedic Fixture

After pre-operative planning for a joint replacement procedure, thetibial preparation system 410 described above can be used to identifythe location and orientation of an axial line, as well as to orient acutting block relative to the axial line.

For example, once the desired varus/valgus and posterior/anterior anglesfor resection have been determined pre-operatively for a kneereplacement procedure, the tibial preparation system 410 can first beassembled as shown in FIG. 4 a. The surgical orientation device 12,coupling mechanism 14, and landmark acquisition assembly 412 can becoupled together, and the landmark acquisition assembly 412 can bepositioned laterally alongside the tibia and outside of the leg.

Similar to the method described above with respect to the landmarkacquisition assembly 312, the secondary rods or structures on thelandmark acquisition assembly 412 can be placed against predeterminedanatomical landmarks alongside the leg, and the surgical orientationdevice 12 can register an orientation of the mechanical axis. Once theorientation of the mechanical axis has been registered, the landmarkacquisition assembly can be positioned and/or aligned in front of thetibia, (i.e. anterior to the tibia)

FIGS. 38 and 39 show the landmark acquisition assembly 412 placed infront of the tibia T. The landmark acquisition assembly 412 can be movedand/or rotated in a first degree of rotation (e.g. roll) until thesensor or sensors 40 in the surgical orientation device 12 observe thatthe roll of the surgical orientation device 12 is aligned withgravitational zero. For example, one axis of a dual-axis accelerometersensor 40 can be aligned with gravitational zero. Once the sensor orsensors 40 inside the surgical orientation device 12 observe that thesurgical orientation device 12 is in this orientation, the surgicalorientation device 12 can provide an indication to the user. Forexample, the surgical orientation device 12 can display zero degrees anda flashing green light on the display 24, or a bubble as describedabove. Once the user has received this indication, the user can press auser input 26 (e.g. a middle button below display 24), confirming and/orregistering the orientation of the surgical orientation device 12.

The landmark acquisition assembly 412 can then be rotated and/or movedin a second degree of rotation (e.g. pitch) until the sensor or sensors40 observe that the surgical orientation device 12 is in a planeparallel to the coronal plane containing the mechanical axis of thepatient's leg. Once the sensor or sensors 40 inside the surgicalorientation device 12 observe that the surgical orientation device 12 isin this orientation, the surgical orientation device 12 can againprovide an indication to the user. For example, the surgical orientationdevice 12 can display zero degrees and a flashing green light on thedisplay 24, or a bubble as described above. Once the user has observedthis light or other indication, the user can press a user input 26 (e.g.a middle button below display 24), confirming and/or registering theorientation of the surgical orientation device 12.

As described above, in some embodiments the surgical orientation devicecan provide an indication when the surgical orientation device 12 isaligned in both degrees of freedom at the same time, rather thanproviding an indication each time separately. Similarly, in someembodiments the user can press the user input 26 once, rather thantwice, to confirm registration of the orientation of the surgicalorientation device 12.

Once the cutting block 84 is aligned with the mechanical axis, theopening 102 which comprises an elongated slot for receiving a cuttingsaw can extend generally perpendicular to the mechanical axis extendingthrough the tibia. If pins were inserted through the cutting block 84into the proximal end of the tibia to anchor the cutting block 84, and acutting saw was inserted through this elongated slot 102, the cuttingsaw would resect the top of the tibia and leave a flat tibial plateauperpendicular to the mechanical axis.

However, as with the other methods described above, the cutting block 84can be adjusted in order to orient the cutting block into thepre-operatively determined varus/valgus and/or posterior/anterior anglesfor resection. For example, the first portion 416 and second portion 418of the landmark acquisition assembly 412 can be separated, and thesecond portion 418 can be placed to the side. The first portion can thenbe moved and/or rotated by hand in a varus/valgus direction and/orposterior/anterior direction.

FIG. 39 shows the landmark acquisition assembly 412 being maneuvered byhand. For example, the handle 414 can be moved towards or away from thedistal end of the tibia in a sagittal plane to move the first portion416 and cutting block 84. This movement can alter the angle of any pinplacement in the cutting block 84, and consequently, alter theposterior/anterior angle of the cutting block 84.

Once the landmark acquisition assembly 412 and cutting block 84 arealigned as desired, a pin or other anchoring device can be insertedthrough a hole 102 of the cutting block 84 and into the tibia, forexample as shown in FIG. 39. This first pin can anchor the cutting blockin place, yet allow the cutting block 84 to swing in a varus-valgusdirection about the first, fixed pin.

The handle 414 can then be used to swing the first portion 416 about thefixed pin, and to orient the cutting block in the varus/valgus plane.For example, a laser system, such as one described above, can be usedwhile the cutting block 84 is pinned and swung by the handle 414. Alaser beam or beams can emanate form the surgical orientation device 12out of the optical element or elements 32. Similar to what is shown inFIGS. 35 a and 35 b, the laser beam can identify a landmark, such as thearea between the first and second toes on the patient's foot, in orderto acquire an orientation of the sagittal plane containing themechanical axis.

Once the orientation of the sagittal plane containing the mechanicalaxis has been acquired and registered in the surgical orientation device12, the handle 414 can be moved again to change the varus/valgus angleuntil the display 24 on the surgical orientation device 12 indicatesthat the varus/valgus angle of the cutting block is at itspre-operatively determined value.

Once the desired pre-operatively determined angles are obtained, asecond pin or pins, or other anchoring device or devices, can be placedthrough the openings 102 in the cutting block 84, and the cutting block84 can be anchored firmly, such that there is substantially no freedomof motion. The handle 414 and rest of first portion 416 can then beremoved completely, leaving only the cutting block 84 securely anchoredto the tibia. A cutting tool (e.g. cutting saw) can then be movedthrough the elongate opening 102 on the cutting block 84 to resect aportion or portions of the proximal tibia.

III. Femoral Cut/Knee Distraction Systems and Methods

As discussed above, knee replacement procedures commonly involve aresection of the tibia along the proximal tibia. This resection of thetibia typically leaves a tibial plateau or plateaus along the proximaltibia, which can provide a location for placement and/or attachment of aprosthetic knee joint.

In addition to a tibial resection, or alternatively to a tibialresection, a knee replacement procedure can further comprise a resectionof a portion or portions of the distal femur. Resecting a portion orportions of the distal femur can provide a location for placement and/orattachment of a femoral knee joint prosthetic. As with the tibialresection, the orientation of a cutting block, and/or cutting plane orplanes, can be pre-operatively determined in order to provide a desiredfit and/or orientation for the femoral knee joint prosthetic. Properlyorientating the cutting plane or planes along the distal femur canfacilitate alignment of the femoral knee joint prosthetic with thetibial knee joint prosthetic. This alignment can create a set of kneejoint prosthetics which function smoothly, continuously, and/or withoutsubstantial wear during their life of use.

Along with attaining and/or facilitating proper alignment between thefemoral knee joint prosthetic and the tibial knee joint prosthetic, theuser can additionally prepare the knee joint such that the ligamentsand/or soft tissue surrounding the knee joint is substantially balancedafter attachment of the knee joint prosthetics. A balanced joint refersgenerally to a joint in which one side of the knee is not substantiallystraining, pulling, and/or constraining the other side of the knee. Forexample, in an unbalanced knee joint, the ligaments and soft tissue onthe lateral side of the knee may be experiencing tension at asubstantially higher degree as compared to the ligaments and soft tissueon the medial side of the knee. During a knee joint replacementprocedure, it can be advantageous to balance the tension on either sideof the knee, so as to prevent undesired strain or stress within the kneejoint. This balancing can be achieved, for example, by use of a kneedistraction device or instrument which distracts the distal femur fromthe proximal tibia in a manner that achieves substantial balancing ofthe knee joint prior to attachment of the knee joint prosthetics.

Systems and methods of preparing a femoral cut, and/or distracting theknee are described further herein. While the systems and methods aredescribed in the context of a knee joint replacement procedure, thesystems and/or their components and methods can similarly be used inother types of medical procedures, including but not limited to shoulderand hip replacement procedures.

A. Femoral Preparation System with a Moveable Orthopedic Fixture

FIG. 5 shows a femoral preparation system 510 for use in a jointreplacement procedure, such as a knee joint replacement procedure. Thefemoral preparation system 510 can be used to resect a portion of afemur, and can comprise the surgical orientation device 12 describedabove, the coupling device 14 described above, and an orthopedicfixture, such as a universal jig 512.

1. Orthopedic Fixture for Orienting a Surgical Orientation Device inMultiple Degrees of Freedom

An orthopedic fixture can be provided which can have a moveable portionor portions which are used to orient a surgical orientation device. Thesurgical orientation device can be oriented in multiple degrees offreedom. For example, FIGS. 40 and 41 illustrate the universal jig 512.The universal jig 512 can be similar to the universal jigs describedabove. For example, the universal jig 512 can comprise a base portion514, a posterior/anterior adjustment block 516, and a varus/valgusadjustment block 518.

The universal jig 512 can facilitate movement of a cutting block in atleast two degrees of freedom. For example, the universal jig 512 can beconfigured to enable the surgeon to move a cutting block in a directionthat changes the angle of the cut on the femur such that the cuttingangle slopes either from the posterior to the anterior side of the kneeor from the anterior to the posterior side (flexion-extension),providing one degree of freedom. The cutting block 512 can additionallyor alternatively be configured so that a cutting block can be moved suchthat the cutting angle slopes in a varus-valgus manner, therebyproviding a second degree of freedom.

In some embodiments, it can be desirable to provide multiple degrees offreedom in a translation direction. For example, the universal jig 512can be configured to enable a cutting block to be moved in a proximal(toward the hip joint) or distal (toward the foot) direction, providinga first degree of freedom in translation. The universal jig 512 canfurther be configured such that a cutting block can be moved posteriorlytoward the surface of the knee joint or anteriorly away from the surfaceof the knee joint to create more space between the block and the joint.In one technique it can be desirable to have the ability to move acutting block posteriorly into contact with the anterior surface of thefemur.

a. Base Member for Providing an Anchored or Fixed Initial Position of anOrthopedic Fixture, and Slide Member for Allowing Translational Movement

A base member can be provided which can anchor or fix an initialposition of an orthopedic fixture. A slide member can also be providedfor allowing translation movement of a portion or portions of theorthopedic fixture. For example, and with continued reference to FIGS.40 and 41, the base member 514 can be attached to a distal portion ofthe femur. For example, a pin, screw, or other anchoring device can beinserted through a hole or holes 520 located along the base member 514.The holes 520 can take any suitable configuration and orientation. Forexample, the holes 520 can be angled at 45° with respect to theposterior surface of the base member 514. Once the anchoring devices areinserted through the base member 514 and into the distal femur, the basemember 514 can be held stable relative to the femur, while otherportions of the universal jig 512 can move relative to the base member514.

The base member 514 can comprise a slot or slots 522 extending along aportion or portions of the base member 514. The slots 522 can beconfigured to receive corresponding, or mating, flanges formed on aslide member 524. For example, the slots 522 can be configured toreceive flanges 526 along slide member 524, as shown in FIG. 41. Theslots 522 and flanges 526 can be configured such that slide member 524can slide and/or translate both distally and proximally relative to thebase member 514 and femur.

The slide member 524 can further comprise receiving holes 528. Thereceiving holes 528 can be sized and/or shaped so as to receive a pivotpin on the posterior/anterior adjustment block 516.

b. Device for Adjusting a Posterior/Anterior Slope of a Cutting Block

A posterior/anterior adjustment device can be provided which can be usedto adjust the orientation of a surgical orientation device and/orcutting block adjacent the femur. For example, the posterior/anterioradjustment block 516 can comprise a pivot pin 530. As described above,the pivot pin 530 can be received by the receiving holes 528 on theslide member 524. The pivot pin 530 can facilitate pivoting motionand/or rotation of the posterior/anterior adjustment block 516 relativeto the slide member 524 and/or base member 514 in a posterior/anteriordirection. In a preferred arrangement, the pivot pin 530 can facilitatepivoting of the posterior/anterior adjustment block 516 within a rangeof approximately twenty degrees (e.g. +−ten degrees on either side of apredetermined angle). Other ranges are also possible.

The posterior/anterior adjustment block 516 can further comprise areceiving hole or holes 532. The receiving holes 532 can be sized and/orshaped so as to receive a pivot pin. The pivot pin can extend throughthe receiving holes 532 as well as through a receiving hole or holes onthe varus/valgus adjustment block 518.

c. Device for Adjusting a Varus/Valgus Slope of a Cutting Block

A varus/valgus adjustment device can be provided which can be used toadjust the orientation of a surgical orientation device and/or cuttingblock adjacent the femur. For example, the varus/valgus adjustment block518 can comprise an elongate rod 534. The elongate rod 534 can extenddistally from the base member 514 when the universal jig 512 is attachedto the distal femur. In a preferred arrangement of the universal jig512, the elongate rod 534 can be coupled to the coupling device 14, andthe coupling device 14 can be couple to the surgical orientation device12.

With continued reference to FIG. 41, the varus/valgus adjustment block518 can further comprise a receiving hole 536. As described above, thereceiving hole 536 can receive a pin which extends through the receivingholes 532. The pin extending through the receiving holes 532 and 536 canfacilitate pivoting motion and/or rotation of the varus/valgusadjustment block 518 relative to the base member 514 in a varus/valgusdirection. In a preferred arrangement, the pivot pin 530 can facilitatepivoting of the posterior/anterior adjustment block 516 within a rangeof approximately twenty degrees (e.g. +−ten degrees on either side of apredetermined angle). Other ranges are also possible.

The varus/valgus adjustment block 518 can further comprise a flange orflanges 538. The flanges 538 can be configured to be received bycorresponding, or mating, slots in a cutting block or other structure.

d. Cutting Block which can be Oriented for Bone Resection

A cutting block, or other orthopedic fixture, can be provided for boneresection. The cutting block can be oriented with the aid of a surgicalorientation device and an orthopedic fixture or fixtures. FIGS. 40 and41 illustrate a cutting block 540. The cutting block 540 can be similarto the cutting block 84 described above. For example, the cutting block540 can comprise at least one opening 102. One opening 102 can comprise,for example, an elongate slot configured to receive a cutting tool, suchas for example a cutting saw.

The cutting block 540 can further comprise a slot or slots 542. Theslots 542 can be configured to receive the flanges 538 on thevarus/valgus adjustment block 518. The combination of the slots 542 andflanges 538 can facilitate movement (e.g. translational movement) of thecutting block relative to the varus/valgus adjustment block 518. Forexample, in a preferred arrangement the cutting block 540 can translatein a posterior/anterior direction (i.e. towards or away from the femur).

B. Acquiring Information Using a Femoral Preparation System

FIGS. 42 and 43 show a method of using the femoral preparation system510. In a preferred arrangement, the base member 514 is first pinned toa distal aspect of the femur F, which has been exposed in anyconventional surgical manner. The orientation device 12 can then becoupled with the elongate rod 534, for example by using the clampingdevice 14. Thereafter, the femoral preparation system 10, including thesurgical orientation device 12, as well as the entire lower leg, can bemoved, swung, and/or pivoted about a proximal head of the femur untilthe location and/or orientation of the mechanical axis of the leg isfound.

For example, the center of rotation of the head of the femur, and/or themechanical axis of the patient's leg, can be detected by moving and/orswinging the leg and attached surgical orientation device 12 on ahorizontal plane (e.g. a plane along the operating table), starting froma known fixed position and orientation (referred to as the origin, whichcan be close to the surface of the horizontal plane) and obtaininginertial readings such as angular displacement and acceleration(referred to as IMU data). The arrows in FIG. 43 illustrate at least oneexample of how the direction or directions the leg can be moved.

The surgical orientation device 12, which can be coupled to the legduring such movement, can comprise at least one single- or multi-axisgyroscope sensor 40 and/or at least one single- or multi-axisaccelerometer sensor 40. The accelerometer(s) can have axes angled withrespect to an axis of the surgical orientation device 12. As the leg isswung, the sensors 42 can detect movement of the surgical orientationdevice 12, and collect the IMU data.

From this IMU data, the surgical orientation device 12 can calculate thelocation of the center of rotation of the femur, as well as the locationof the mechanical axis running through the leg.

Once the surgical orientation device 12 has made the above-describedcalculation or calculations, the surgical orientation device 12 can berotated and/or moved by the universal jig 512 to align the surgicalorientation device 12 with the mechanical axis of the leg. When thesurgical orientation device 12 is aligned with the mechanical axis ofthe leg, the surgical orientation device 12 can provide a signal, suchas for example a flashing green light on its display 24.

The user can then use the universal jig 512 to move and/or change theposition of the surgical orientation device 12 and cutting block 540, inorder to achieve a pre-operatively determined resection angle or anglesfor resection of the femur. As with the tibial cut methods describedabove, the varus/valgus and posterior/anterior angles for resection canbe adjusted by moving the varus/valgus adjustment block 518 and/orposterior/anterior adjustment block 516. Other adjustments, movements,translations, rotations, and/or changes in position of the cutting block540 can also be made.

The surgical orientation device 12 can provide an indication of degreesof movement. For example, the surgical orientation device 12 can informthe user how many degrees (e.g. in half degree increments) the surgicalorientation device and cutting block 540 are rotated past the mechanicalaxis in one or more planes. The surgical orientation device can displaythis information in its display 24, and/or provide audio indications tothe user as well.

The cutting block 514 can then be brought into contact with the distalfemur. The cutting block 540 can be immobilized, for example, byadvancing pins through one or more openings 102. The user can thendisconnect the surgical orientation device 12 from the universal jig512, e.g. by releasing the clamping device 14. Additionally, oralternatively, the user can disconnect a portion or portions of theuniversal jig 512 from the cutting block 540, thereby leaving thecutting block 540 behind on the distal femur. Thereafter, the cuttingblock 540 can be used to resect the distal femur. For example, a cuttingtool or tools can be moved through an elongate opening or openings 102,so as to prepare the distal femur for receiving a knee joint prosthetic.

C. Alternative Method of Using Femoral Preparation System

In other embodiments, the center of rotation and the mechanical axis canbe detected by moving the leg about the junction of the femoral head andan acetabulum in several different planes, as opposed to one plane, andobtaining IMU inputs of the femur for various locations of the distalend of the femur approximating a portion of a spherical surface, withthe center of the sphere being the femoral head center. For example, inone embodiment of the surgical orientation device 12 incorporating oneor more multi-axis accelerometers and gyroscopes, IMU data for eachmovement of the femur can be numerically integrated over time to obtaina trajectory of position and velocity points (one point for each IMUinput) without imposing any plane trajectory constraints on movements ofthe femur. The location of the sphere center (e.g., the femoral headcenter) can be calculated using, for example, a non-linear least-squaresfit algorithm. Examples of three possible leg movement trajectories forcalculating IMU data are: (i) a horizontal swing from the leg's positionof origin to the surgeon's right and then back again; (ii) a horizontalswing from the origin to the surgeon's left and then back again; and(iii) a vertical swing upward and then back again. During each swingtrajectory the IMU data can be stored for future processing.

Accuracy in determining the femoral head center can be improved if bothpositive and negative time integrations are performed for each movementof the femur from an origin at t=T0 to a given position at t=T1 and thenback again to the origin at t=T2. The negative integrations (whichcorrespond to integration from T2 to T0 in one technique) can be used toreduce the integration errors which may arise, for example, because ofimperfect calibration or drift. For example, following each inertialmeasurement for a given location of the distal femur, the leg can bereturned to its origin, with input provided to the surgical orientationdevice 12 that the surgical orientation device 12 has been returned tothe origin. In one embodiment, the surgical orientation device 12 can beconfigured to assume or recognize that it has been returned to theorigin. The surgical orientation device 12 can include a microcontrollerin its electronic control unit 1102, for example, that can be configuredto perform forward and backward integration over the maneuver andcompare the results. This can be done as a way to calibrate the sensors40.

When taking inertial readings, the surgical orientation device 12 canassume that roll motion of the femur (with respect to a femur line) iszero. In one method, the user can restrict the femur roll motion as muchas possible and endeavor to move the femur in pitch and yaw motions(with respect to the femur line) when taking readings.

In one embodiment, the surgical orientation device 12 can be placed atthe origin with no motion for a pre-determined time period to signalpositioning at the origin, e.g., at least one second in between swingtrajectories. This can facilitate the surgical orientation device'srecognition of the start and end of a swing trajectory. In such anembodiment, a numerical value for magnitude of the acceleration ofgravity or the location of the device in an Earth Centered Rotating(ECR) coordinate system can be an input to the processing inside theelectronic control unit 1102.

In one embodiment of the device, there can be a parameterized functionmapping of the IMU readings to the assumed or estimated acceleration andangular orientation in a frame attached to the device. This set oftrajectory points (i.e. free trajectory points) along with the set IMUreadings can be referred to as spherical independent values. There canbe four individual dynamic sets of independent values, which are:position, velocity, IMU gyro values, and IMU accelerometer values.During the processing, a corresponding set of spherical dependent valuescan be generated, assuming the motion of the surgical orientation device12 is constrained to the surface of the sphere and there is no rollmotion about the line connecting the center of the sphere and thesurgical orientation device 12. This set of values can be a function ofthe center of the sphere (the value for the radius of the sphere can beknown since the origin is assumed to lie on the surface of the sphere)and, if needed, a set of IMU calibration parameters. The assumption canbe made that at each IMU cycle time the surgical orientation device 12is at a point of intersection of the sphere and the line connecting thecorresponding independent position point and the center of the sphere.

The algorithm employed by the surgical orientation device 12 todetermine the femoral head center can utilize a mathematical principlethat determines the values for the unknown parameters (femoral headcenter and IMU calibration parameters) that minimize a cost functionconsisting of the sum of the squares of the difference between thespherical independent values and the spherical dependent values. Thespherical independent IMU values can be provided by the sensor orsensors 40, and the spherical dependent IMU values can be calculated.

The following are two Cartesian coordinate frames that may be used todescribe an algorithm:

-   -   1. The inertial Trajectory frame or T-frame. The coordinate        frame for integrating the IMU input values. The origin is at the        center of device at the start and end of each trajectory and the        unit vectors are        -   Z-axes (Z_(T)) points upward        -   X-axes (X_(T)) points in patients foot to head in the            horizontal plane        -   Y-axes (Y_(T)) points to the surgeons left in the horizontal            plane (Y_(T)=Z_(T)×X_(T)).    -   2. The moving and rotating Device frame or D-frame. The IMU        system can be attached to this frame and its origin can be        located at the center of the IMU device. At the start/end of        each frame it should be aligned with the T-frame.        -   X-axes (X_(D))=(X_(T))        -   Y-axes (Y_(D))=(Y_(T))        -   Z-axes (Z_(D))=(Z_(T))

The following symbols can be used to describe the processing thatgenerates the spherical independent trajectory points for the nth swingtrajectory according to one technique that can be incorporated into anembodiment of an orientation device described herein.

Δ—IMU cycle time intervalt_(n) ⁰—Starting time of the trajectoryt_(n) ^(I)—Ending time of the Ith IMU cycle (I*Δ).N_(n) ^(I)—Total number of trajectory IMU time intervals.t_(n) ^(E)—Trajectory ending time (N_(n) ^(I)*Δ)w_(n)(t)—IMU angular velocity input value for time tw_(n) ^(I)—IMU angular velocity input value for cycle I (w_(n)(t)=w_(n)^(I) for (I−1)*Δ<t≦I*Δ)a_(n)(t)—IMU acceleration input value for the nth swing at time t.a_(n) ^(I)—IMU angular velocity input value for cycle I (a_(n)(t)=a_(n)^(I) for (I−1)*Δ<t≦I*Δ)W_(D)(x_(w),w(t))—The function that maps the IMU angular velocity valueto the assumed/estimated angular velocity in the D-frame.x_(w)—Gyro calibration parameters that can be estimated such as biasesand scale factors.N_(w)—Number of Gyro calibration parameters (can be zero)Φ_(D) ^(T)(t): Direction Cosine matrix—maps a vector in the D-frame to avector in the T-frame. It can be calculated using both forward andbackward time integration

${{{}_{\;}^{}{}_{}^{}}(t)} = {I_{3} + {\int_{t^{0}}^{t}\left( \ {{{{{{}_{\;}^{}{}_{}^{}}(t)} \cdot {W_{D}\left( {x_{w},{w(s)}} \right)}} \times {{{}_{\;}^{}{}_{}^{}}(s)}{s}{{{}_{\;}^{}{}_{}^{}}(t)}} = {I_{3} + {\int_{t^{E}}^{t}\left( \ {{{{{{}_{\;}^{}{}_{}^{}}(t)} \cdot {W_{D}\left( {x_{w},{w(s)}} \right)}} \times {{{}_{\;}^{}{}_{}^{}}(t)}(s){s}I_{3}} = \begin{pmatrix}1 & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1\end{pmatrix}} \right.}}} \right.}}$

A_(D) (x_(A),a(t))—The function that maps the IMU accelerometer value tothe assumed/estimated acceleration in the D-frame.x_(A): Accelerometer calibration parameters that may need to beestimated such as biases and scale factors.N_(A)—Number of Accelerometer calibration parameters (can be zero).⁺R_(n) ^(I)(x_(A),x_(W))—Ith positive trajectory position point⁻R_(n) ^(I)(x_(A),x_(W))—Ith negative trajectory position point⁺V_(n) ^(I)(x_(A),x_(W))—Ith positive trajectory velocity point⁻V_(n) ^(I)(x_(A),x_(W))—Ith negative trajectory velocity point

⁺ R _(n) ^(I)(x _(A) ,x _(W))=∫₀ ^(t) ^(I) ∫₀ ^(t) A _(T)(x _(w) ,x _(A),w _(n)(s),a _(n)(s))dsdt

⁻ R _(n) ^(I)(x _(A) ,x _(W))=∫_(Tn) ^(t) ^(I) ∫_(Tn) ^(t) A _(T)(x _(w),x _(A) ,w(s),a(s))dsdt

⁺ V _(n) ^(I)(x _(A) ,x _(W))=∫₀ ^(t) ^(I) A _(T)(x _(w) ,x _(A) ,w_(n)(s),a _(n)(s))ds

⁻ V _(n) ^(I)(x _(A) ,x _(W))=∫_(Tn) ^(t) ^(I) A _(T)(x _(w) ,x _(A) ,w_(n)(s),a _(n)(s))ds

A _(T)(x _(w) ,x _(A) ,w _(n)(s),a _(n)(s))=Φ_(D) ^(T)(x _(w) ,s)·A_(D)(x _(A) ,a _(n)(s))

R_(n) ^(I)(x_(A),x_(W)) Ith trajectory position point.

R _(n) ^(I)(x _(A) ,x _(W))=β⁺*(⁺ R _(n) ^(I)(x _(A) ,x _(W)))+(1−β⁺)*(⁻R _(n) ^(I)(x _(A) ,x _(W)))

β⁺=(t _(n) ^(E) −t _(n) ^(I))/t _(n) ^(E)

Error in double integration due to white is proportional to the time ofintegration.

V_(n) ^(I)(x_(A),x_(W))—The Ith trajectory velocity point

V _(n) ^(I)(x _(A) ,x _(W))=β⁺*(⁺ V _(n) ^(I)(x _(A) ,x _(W)))+(1−β⁺)*(⁻V _(n) ^(I)(x _(A) ,x _(W)))

β⁺=((t _(n) ^(E) −t _(n) ^(I))/t _(n) ^(E))^(1/2)

Error in single integration due to white is proportional to thesquare-root of time of integration.

The following describes a processing for the spherical dependenttrajectory parameters. Most of the calculation can be performed in theInertial Trajectory Frame. This processing assumes the points areconstrained to the surface of a sphere. The center of the sphere isdenoted by {right arrow over (R)}c or the three component vector(x_(c),y_(c),z_(c)). Since the origin is assumed to be on the sphere theradius of the sphere is

Rc=(x _(c) ² +y _(c) ² +z _(c) ²)^(1/2)

The following symbol and expression are use to describe how the Ithspherical dependent trajectory parameter values can be calculated interms of the (I−1)th values for the nth swing trajectory.

^(S)R_(n) ^(I)—Ith position point

^(S) R _(n) ^(I)=unit(R _(n) ^(I))*Rc

^(S)θ_(n) ^(I)—Ith rotation vector

^(S)θ_(n) ^(I)=unit(^(S) R _(n) ^(I-1)×^(S) R _(n) ^(I))*arccos(unit(^(S) R _(n) ^(I-1))·unit(^(S) R _(n) ^(I)))

^(S)Ω_(n) ^(I)—Ith angular velocity vector

^(S)Ω_(n) ^(I)=^(S)θ_(n) ^(I)/Δ

^(S)V_(n) ^(I)—Ith velocity point

^(S) V _(n) ^(I)=Ω_(n) ^(I)×^(S) R _(n) ^(I)

^(S)A_(n) ^(I)—Ith acceleration vector

^(S) A _(n) ^(I)=(^(S) V _(n) ^(I)−^(s) V _(n) ^(I-1))/Δ

^(S)Φ_(n) ^(I)—Ith Spherical Trajectory direction cosine matrix;transforms a vector in the Device frame to a vector in the Trajectoryframe.

${{{}_{\;}^{}{}_{}^{I\text{-}1}} = {{{}_{\;}^{}{}_{}^{}} \otimes {{}_{\;}^{}{}_{}^{I\text{-}1}}}};{{{}_{\;}^{}{}_{}^{}} = \begin{pmatrix}1 & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1\end{pmatrix}}$

The operator “

” produces the direction cosine matrix that results from rotating thedirection cosine matrix to the right of the operator about the angle tothe left of the operator.

_(D) ^(S)Ω_(n) ^(I)—Ith angular velocity vector for the nth swingtrajectory expressed in the device frame

_(D) ^(S)Ω_(n) ^(I)=½*(^(S)Φ_(n) ^(I-1)+^(S)Φ_(n) ^(I))^(T)·^(S)Ω_(n)^(I)

_(D) ^(S)A_(n) ^(I)—Ith acceleration vector expressed in the deviceframe

_(D) ^(S) A _(n) ^(I)=½*(^(S)Φ_(n) ^(I-1)+^(S)Φ_(n) ^(I))^(T)·^(S) A_(n) ^(I)

^(S)w_(n) ^(I): Ith calculated gyro value (the application of theinverse mapping of the gyro calibration function)

^(S) w _(n) ^(I) =W _(D) ⁻¹(x _(w),_(D) ^(S)Ω_(n) ^(I))

^(S)a_(n) ^(I): Ith calculated gyro value (the application of theinverse mapping of the accelerometer calibration function)

^(S) a _(n) ^(I) =A _(D) ⁻¹(x _(a),_(D) ^(S) A _(n) ^(I))

The following contains a definition of the four trajectory parametercost functions and the total cost function. The total cost functionrepresents a weighted average of the four trajectory parameter costfunctions.

γ_(R)(x_(c),y_(c),z_(c),x_(A),x_(W))—Position Cost Function

$\gamma_{n}^{R},{\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right) = \left( {\sum\limits_{I = 1}^{N_{n}^{I}}{{{{}_{\;}^{}{}_{}^{}} - R_{n}^{I}}}^{2}} \right)}$${\gamma_{R}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)} = {\sum\limits_{n = 1}^{N_{T}}{\gamma_{n}^{R}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)}}$

γ_(V)(x_(c),y_(c),z_(c),x_(A),x_(W))—Velocity Cost Function

$\gamma_{n}^{V},{\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right) = \left( {\sum\limits_{I = 1}^{N_{n}^{I}}{{{{}_{\;}^{}{}_{}^{}} - V_{n}^{I}}}^{2}} \right)}$${\gamma_{V}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)} = {\sum\limits_{n = 1}^{N_{T}}{\gamma_{n}^{V}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)}}$

γ_(G)(x_(c),y_(c),z_(c),x_(A),x_(W))—Gyro Cost Function

$\gamma_{n}^{G},{\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right) = \left( {\sum\limits_{I = 1}^{N_{n}^{I}}{{{{}_{\;}^{}{}_{}^{}} - w_{n}^{I}}}^{2}} \right)}$${\gamma_{G}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)} = {\sum\limits_{n = 1}^{N_{T}}{\gamma_{n}^{G}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)}}$

γ_(A)(x_(c),y_(c),z_(c),x_(A),x_(W))—Accelerometer Cost Function

$\gamma_{n}^{A},{\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right) = \left( {\sum\limits_{I = 1}^{N_{n}^{I}}{{{{}_{\;}^{}{}_{}^{}} - a_{n}^{I}}}^{2}} \right)}$${\gamma_{A}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)} = {\sum\limits_{n = 1}^{N_{T}}{\gamma_{n}^{A}\left( {x_{c},y_{c},z_{c},x_{A},x_{W}} \right)}}$

γ(x_(c),y_(c),z_(c),x_(A),x_(W))—Total Cost Function

γ(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W))=α_(R)*γ_(R)(x _(c) ,y _(c) ,z_(c) ,x _(A) ,x _(W))+α_(V)*γ_(V)(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x_(W))+α_(G)*γ_(G)(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W))+α_(A)*γ_(A)(x_(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W))

The mathematical goal of the algorithm can be to solve the following3+Na+Nw equations for (x_(c),y_(c),z_(c),x_(A),x_(W)) that minimize theTotal Cost Function.

∂γ(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W))/∂x _(c)=0

∂γ(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W))/∂y _(c)=0

∂γ(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W))/∂z _(c)=0

∇x _(A)(γ(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W)))=0, ∇x _(A) thegradient wrt accelerometer calibration parameters

∇x _(W)(γ(x _(c) ,y _(c) ,z _(c) ,x _(A) ,x _(W)))=0, ∇x_(W) thegradient wrt gyro calibration parameters

D. Femoral Preparation System with Knee Distraction Device for Resectingthe Femur and/or Distracting the Knee Joint

A femoral preparation system can be provided which can both align acutting block for resecting a bone, as well as distract a joint so as tobalance the tissue surrounding the joint. For example, FIG. 6 shows afemoral preparation system 610 for use in a joint replacement procedure,such as for example a knee joint replacement procedure. The femoralpreparation system 610 can comprise the surgical orientation device 12described above, the coupling device 14 described above, and adistraction instrument, such as for example a knee distraction device612. As described further herein, the femoral preparation system 610 canbe used for both alignment and distraction.

FIG. 44 shows a knee distraction device 612. The knee distraction device612 can be configured to distract the knee joint during a kneereplacement procedure and balance the soft tissue and/or ligamentswithin the knee joint. The knee distraction device 612 can additionallyor alternatively be configured to facilitate attachment of a cuttingblock to the distal femur for resection of the distal femur.

With continued reference to FIG. 44, the knee distraction device 612 cancomprise a distractor body, such as for example a body 614. The body 614can comprise an inner body portion 616, an outer body portion 618, andat least one adjustment device 620. The knee distraction device 612 canfurther comprise a reference feature, such as for example a tibialbaseplate 624, and at least one distraction element 626. The kneedistraction device can further comprise guide portion 628. The body 614,tibial baseplate 624, and distraction element or elements 626 can forman anterior portion of the knee distraction device 612.

In some embodiments the distraction elements 626 can comprise femurcontacting components. For example, the distraction elements 626 caninclude generally flat, thin, foot portions 630 which extend away fromthe body 614, and can be configured to engage the bottom of a bonylandmark, such as for example a femoral condyle. The distractionelements 626 can further include posts 632 which can be movable relativeto the tibial baseplate 624, and can extend into a portion or portionsof the outer body portion 618.

The posts 632 can be controlled by the adjustment devices 620 on eitherside of the body 614. The adjustment device or devices 620 can compriseknobs, and the distraction elements 626 can resemble feet, with legswhich extend from a lower, or distal, portion of the body 614.

The tibial baseplate 624 can comprise a planar member coupled to thedistractor body, and can sit underneath the distraction elements 626.The tibial baseplate can be configured to be positioned on a tibialplateau. The tibial baseplate 624 can extend at an angle perpendicularto a front face of the body 614. The distraction elements 626 can becoupled with the distractor body, and can be configured to be movedrelative to the tibial baseplate 624 to increase or decrease a gaptherebetween. The distraction elements 626 can also extend at an angleperpendicular to the front face of the body 614, and can individually bemoved away from the tibial baseplate 624 (e.g. in a proximal direction),or towards the tibial baseplate 624 (e.g. in distal direction), byturning the adjustment devices 620.

FIG. 45 shows a side view of the knee distraction device 612. As shownin FIG. 45, the knee distraction device 612 can comprise a sizing stylus622. The stylus 622 can form a posterior portion of the knee distractiondevice 12, and can be a modular device that can be changed toapproximate a desired femoral implant size and/or to accommodateanatomical differences between the left and right knee joints. Thestylus 622 can reference a particular femoral implant size and acorresponding measurement along an anterior aspect of the femur. Thestylus 622 can generally comprise an anterior/posterior (A/P) sizingguide, and in some embodiments can include a marking or markings 634along an attached post. The marking or markings 634 can provide anindication of how far the stylus 622 has been raised or lowered relativeto, for example, the distraction element 626. The stylus 622 can beattached to, and/or move with, the inner body portion 616. The stylus622 can be used, for example, to help measure the needed size of a kneejoint prosthetic during a knee joint replacement procedure.

The body 614 of the knee distraction device 612 can further comprise asecuring device 636. The securing device 636 can comprise, for example,a knob which can be turned to lock the guide portion 628 in place. Whenunlocked, the guide portion 628 can slide within an opening of the outerbody portion 618.

In some embodiments, the guide portion 628 can protrude at least 75 mmbeyond the tibial baseplate 624. In some embodiments, the guide portion132 can be 12.7 mm in diameter. Other diameters are also possible. Insome embodiments, a cross section of the guide portion 628 can comprisea generally round portion and a generally flat portion similar to theprimary rod 316 of the landmark acquisition assembly 312 describedabove. A portion of the guide portion 628 can be used, for example, as ahandle. The guide portion 628 can be used to couple the knee distractiondevice 612 to the surgical orientation device 12. For example, thecoupling device 14 can be attached to the guide portion 628, and thesurgical orientation device 12 can be attached to the coupling device14.

FIGS. 44, 45, and 46 illustrate how the inner body portion 616, outerbody portion 618, and posts 632 can function together. FIG. 44 shows achannel 638 extending down the outer body portion 618 on either side ofthe outer body portion 618. The posts 632, which are shown extendingfrom beneath the outer body portion 618 in FIG. 44, can extend up intothese channels 638.

FIG. 45 shows a top view of the knee distraction device 612, lookingdown the channels 638. As illustrated, the tops of posts 632 can be seeninside the channels 638. FIG. 45 also shows extrusions 640. Theextrusions 640 can form part of the inner body portion 616, and canextend partially or entirely into the channels 638.

FIG. 47 shows the knee distraction device 612 with the outer bodyportion 618 removed. The extrusion 640, which extends from inner bodyportion 616, can rest on top of the post 632, such that as the post 632is moved inside the channel 638, the inner body portion 616 is moved aswell. In some embodiments, the adjustment device 620 and post 632 cancomprise a rack and pinion-like gear system, wherein the post 632comprises a plurality of gear teeth, and the adjustment device 620comprises a plurality of corresponding gear teeth. When the adjustmentdevice 620 is turned, the post 632 can be moved either up or down (e.g.proximally or distally) within the channel 638. As the post 632 moves,the post 632 can carry the inner body portion 640, and stylus 636, withit. In some embodiments, only one extrusion 640 can be used to dictateand/or facilitate movement of the inner body portion 616.

With continued reference to FIG. 47, the inner body portion 616 cancomprise a modular structure or device, such as for example a sizingguide, which can be used for a specifically-sized implant or implants,and/or for a right leg or left leg only. In some embodiments, the innerbody portion 616 can be removable from the knee distraction device 612.The inner body portion 616 can be used to measure femoral implant size,and can contain holes through which pins can be placed into the femur(or other bony structure) for mounting another surgical apparatus orapparatuses.

In a preferred arrangement of the knee distraction device 612, movementof the post or posts 632 can be tracked or monitored. For example, theknee distraction device 612 can provide audible and/or visual feedbackto the user, indicating the degree or extent to which a post 632 anddistraction element 626 have been moved relative to an initial startingposition. FIG. 48 shows a pin 642 and spring 644 which can be insertedinto the outer body portion 618. The spring 644 can bias the pin 642against gear teeth along the post 632, such that as the post 632 movesup and/or down, a user can hear and/or feel an edge of the pin 642contacting the gear teeth along the post 632. This contact can producean audible click, or clicks. This contact can additionally oralternatively provide a force (e.g. frictional) which can hold the post632 in a desired position, until the adjustment device 620 is turnedagain.

With continued reference to FIGS. 44-48, the distraction elements 626,including the foot portions 630, can be moved up and down (e.g.proximally and distally) relative to the tibial baseplate 624 by theadjustment device or devices 626. For example, the distraction elements626 can be moved individually and independently in a vertically upwards(e.g. proximal) direction to apply pressure to the distal condyles of afemur or other bony structure in the body, and move the condyles of thefemur to a desired position. This movement can distract the knee joint,surrounding soft tissue, and/or ligaments. In some embodiments, apressure or force gauge or gauges can be incorporated with the kneedistraction device 612 to determine the amount of compressive forcewhich was applied by, or is being applied by, the distraction elements626 against the condyles of the femur.

The knee distraction device 612 can include an indicator which indicatesthe distance the inner body portion 616 has traveled relative to thetibial baseplate 624 after the adjustment device or devices 20 has beenturned. For example, the indicator can be in the form of markings and/orother structures or components which provide a visual or audioindication.

The knee distraction device 612 can further comprise a spring or springswhich can apply a constant spring force to whatever anatomical structureor structures the distraction elements 626 are contacting. For example,each distraction element 626 can include a pre-tensioned spring, suchthat when the knee distraction device 612 is placed into an anatomicaljoint (e.g. a knee joint), the pre-tensioned springs can be released,and a constant, pre-determined pressure can be applied by thedistraction elements 626 to any contacted anatomical structures (e.g.condyles). In some embodiments, the pressure applied can beapproximately 70-80 psi. In other embodiments the pressure applied bycan be approximately 60-90 psi. Other pressures and/or pressure rangesare also possible. The pressures applied by each spring can bedifferent.

In some embodiments, when the knee distraction device 612 is being usedto distract the knee joint, a ligament or ligaments can be released oneither or both sides of the knee. The knee distraction device 100 can beused to modify the ligament(s) of the knee to provide a desired balanceof forces around the knee joint.

In a preferred arrangement, the foot portions 630 can be removablyattached to the posts 632. The foot portions 630 can be adjustablerelative to the body 614 and/or posts 632. For example, the footportions 630 can be longitudinally slotted, such that the foot portions630 can be adjusted in a longitudinal direction in a plane containingthe tibial baseplate 624. This adjustment can allow the foot portions630 to be inserted into a knee joint, or other joint, at differentdepths, for example based on the knee joint size. By making the footportions 630 slotted and/or adjustable relative to the posts 632, thefoot portions 630 can be inserted to a particular desired depth duringeach step of a procedure. Furthermore, the adjustability of the footportions 630 can enable a single pair of foot portions 630 to be usedthroughout a joint procedure. In other contexts, a plurality of depthscan be achieved by providing a set of foot portions 630 of differentlengths that can be coupled with the posts 632.

In a preferred arrangement, the foot portions 630 can additionally berotatably adjustable. For example, the foot portions 636 can rotate inone or more directions about the posts 632. This rotation can facilitateuse of the knee distraction device 612 in knee joints which vary insize, and where for example the femoral condyles in a particular kneejoint are spaced significantly far apart. This rotation can also allowthe foot portions 630 to be inserted through a relatively narrowincision in the body and then spread out once inside the knee joint(e.g. rotate away from one another) to engage the femoral condyles. Thisrotation can inhibit the use of larger, more undesirable incisions on apatient's body, thereby leaving the patient with a smaller, less visiblescar after a joint replacement procedure.

FIG. 47 illustrates an opening or openings 646. The openings 646 can belocated on the inner body portion 616, and can extend through the entireinner body portion 616. While eight such openings 646 are shown in FIG.47, different numbers, sizes, shapes, and/or locations of openings 646can also be used.

The openings 646 can be used as drill hole and/or pin insertion guides.For example, when the knee distraction device 612 has distracted adistal femoral condyle or condyles in a knee replacement procedure, apin or pins can be inserted into the distal femur in order to provide amounting location for a cutting block. The openings 646 can be used asguides for insertion of these pins. The openings 646 can be spaced apartfrom one another in a pattern or patterns. For example, some of theopenings 646 along the bottom of the inner body portion 616 can bespaced slightly higher, and/or further away from the tibial baseplate624 than other openings 646 along the bottom of the inner body portion616. Similarly, some of the openings 646 along the top of the inner bodyportion 616 can be spaced slightly higher, and/or further away from thetibial baseplate 624 than other openings along the top of the inner bodyportion 616. This spacing can be used, for example, to eventuallycontrol the orientation of a cutting block which is later attached tothe pins.

The knee distraction device 612 described above can be biocompatible forshort term exposure to the inner anatomy of the knee or other bodyjoint, and can be sterilized by autoclave and/or gas. The weight of theknee distraction device 612 can vary. For example, in a preferredarrangement, the knee distraction device 612 can have a maximum weightof 1 kg, and can generally be lightweight for ease of operation andhandling. Other maximum weights, including weights greater than 1 kg,are also possible.

The knee distraction device 612 can operate without lubricants.Materials can be selected and treated to prevent galling and providesmooth operation consistent with expectations for a high qualitysurgical instrument. In general, the knee distraction device 612described above can be made robust to withstand normal and abusive use,especially rough handling during cleaning and/or sterilization. The kneedistraction device 612 can be etched with part numbers, revisionslevels, and company name and logo. Other markings can be added toprovide clarity.

The knee distraction device 612, or other similar distraction devices,can be used in joints other than the knee joint. For example, the kneedistraction device 612 can be used in the elbow, or other joint, todistract a joint.

E. Acquiring Orientation Information and Distracting a Joint Using aFemoral Preparation System

During a knee joint replacement procedure, the knee distraction device612 and femoral preparation system 610 described above can be used toalign and balance the ligamentous structure of the knee joint and/ordetermine an orientation for a cut or cuts along the femur. In sometechniques, one cut is referred to as the distal femoral cut (DFC). TheDFC removes a distal (i.e., lower) portion of the femur.

Prior to using the femoral preparation system 610, and prior to the DFC,the proximal (i.e. upper) tibia can be cut. For example, and asdescribed above, a tibial preparation system 10, 210, 310, 410, or othertibial preparation system can be used to resect a portion or portions ofthe tibia, such that the proximal end of the tibia comprises generally aflat plane or plateau. Based on pre-operative determinations of desiredvarus/valgus, posterior/anterior, and/or other angles for this tibialresection plane, the plateau can be perpendicular to the mechanicalaxis, or at an angle other than perpendicular to the mechanical axis.

Prior to insertion of the knee distraction device 612 into the kneejoint, an appropriately sized and/or configured inner body portion 616can be chosen. For example, the inner body portion 616 can indicate“LEFT” for a left leg and “RIGHT” for a right leg. Additionally, priorto insertion of the knee distraction device 612, osteophytes on thefemur and/or tibia can be removed to prevent obstruction andinterference.

FIGS. 49 a and 49 b show the leg in full extension, with a portion ofthe knee distraction device 612 inserted into the knee joint. Thedistraction elements 626 are shown inserted underneath the femoralcondyles, and above the tibial plateau, such that one distractionelement 626 is located generally underneath one condyle, and anotherdistraction element 626 is located generally under the other condyle.The tibial baseplate 624 is also shown inserted into the knee joint.

Prior to or after insertion of the knee distraction device 612, thelaser 42 of the surgical orientation device 12 can be turned on, suchthat a laser beam or beams emanate from the optical element or elements32. For example, and as shown by the arrow in FIG. 49 a, the user canpress one of the user inputs 26. The laser beams are illustrated indashed lines in FIGS. 49 a and 49 b.

With reference to FIGS. 49 a, 49 b, 50 a, and 50 b, once a portion ofthe knee distraction device 612 is inserted into the knee joint, thedistraction elements 626 can be moved up or down by turning theadjustment devices 620. For example, the distraction elements 626 can bemoved away from the tibial baseplate 624 and into contact with distalaspects of the femoral condyles, thereby causing the knee distractiondevice 12 to apply an opposing force or forces to the proximal tibia andthe distal aspect of the femoral condyles. This force or forces candistract the knee joint and its surrounding soft tissue and/orligaments. Each distraction element 626 can be moved independently, andas described above, if desired each distraction element 626 can apply adifferent amount of pressure or force to each femoral condyle. In apreferred arrangement, and as described above, as a distraction element626 moves, the distraction element 626 can cause identical movement ofthe inner body portion 616. In other embodiments, the inner body portion616 can remain stationary while the distraction elements 626 are moved.

With continued reference to FIGS. 49 a, 49 b, 50 a, and 50 b, the laserbeam or beams emanating from the surgical orientation device 12 canprovide an indication of, and/or facilitate, alignment of the femoralpreparation system 610. For example, while the distraction elements 626are being moved and/or adjusted, and the knee joint is being distracted,the laser beams can move towards a desired anatomical landmark orlandmarks. As shown in FIG. 50 b, one of these landmarks can be on thehip and/or femoral head, and the other can be on the foot and/or ankle.These landmarks can be used to identify an orientation of the mechanicalaxis. For example, if the laser beams are pointing to one or more ofthese landmarks, the user can have a visual indication that the surgicalorientation device 12 is generally aligned with the mechanical axis. Theuser can also have a visual indication that a gap, or distance, betweenone femoral condyle and the tibial plateau is substantially identical tothe gap, or distance, between the other femoral condyle and the tibialplateau. In some embodiments, the user can release one or more ligamentsin the knee joint prior to or during the knee distraction in order tofacilitate simultaneous symmetry of the gaps, mechanical axis alignment,and/or balancing of the soft tissue and/or ligaments in the knee joint.

During distraction, the surgical orientation device 12 can be configuredto measure and display tension within the soft tissue on the medialand/or lateral sides of the knee joint. For example, the kneedistraction device 612 can comprise sensors, or other structures, whichcan relay information to the surgical orientation device about thedegree of tensile force being exerted upon the distraction element orelements 626, and/or the tibial baseplate 624. The surgical orientationdevice 12 can display this information, for example, on the display 24.If the tension on a medial or lateral side of the knee is too great, theuser can change the tension by adjusting (e.g. turning) one or more ofthe adjustment members 620.

Once the distraction elements 626 have applied a desired level ofpressure or force against the condyles of the femur, and/or the femoralpreparation system 610 is aligned with the mechanical axis (or otheraxial line), a drill or other cutting tool can be used to drill holesthrough the openings 646 of the knee distraction device 612 into thefemur. In some embodiments, the openings 646 closest to the outer bodyportion 618 can be used. In other embodiments, different sets ofopenings 646 can be used. The openings 646 which are selected candetermine and/or change an orientation and/or arrangement of referencepins which are placed into the femur. This orientation and/orarrangement of reference pins can determine the orientation of a cuttingblock which can be attached to the reference pins after the femoralpreparation system 10 is removed. For example, if the user haspre-operatively determined that a cutting plane along the distal femurshould be oriented at three degrees in a varus/valgus direction relativeto the mechanical axis, the user can select a set of openings 646 whichprovide for a three degree slope, and drill holes through these openings646.

These drilled holes can serve as reference holes, and can be used forinsertion of reference pins 647. As shown in FIGS. 51 a and 51 b, thereference pins 647 can be inserted through the openings 646 and into thereference holes in the femur. Once the reference pins are inserted intothe femur, the femoral preparation system 610 can be removed, and acutting block 648. The cutting block 648 can be placed onto or coupledto the reference pins. As shown in FIG. 52, once the cutting block 648is attached, a saw or other cutting device can then be used to make anappropriate DFC cut or cuts of the femur.

In some knee joint procedures, another cut which can be made is aposterior femoral cut (PFC). In preparation for the posterior femoralcut, the leg can be placed in approximately 90 degrees of flexion. FIG.53 shows the leg in flexion, with the tibial baseplate 624 anddistraction elements 626 again extended inside the knee joint. The body614 of the knee distraction device 612 can sit flush with a plateauformed on the resected femoral condyles from the DFC.

Once the knee distraction device 612 is inserted into the knee joint,the adjustment devices 626 on either side of the outer body portion 618can be turned to individually move the distraction elements 626 awayfrom the tibial baseplate 624, thereby distracting the knee joint andapplying an individual opposing force or forces to the tibial plateauand the femoral condyles. Each condyle can be distracted individually,simultaneously, and/or consecutively.

FIGS. 53, 54, and 55 show the knee distraction device 612 duringadjustment of the distraction elements 626. As shown in FIGS. 54 and 55,the user can activate the laser 42 on the surgical orientation device 12to facilitate alignment of the surgical orientation device 12 with themechanical axis. For example, the knee distraction device 12 can beadjusted until a laser hits a landmark such as the area between thefirst and second toe on the patient's foot.

As shown in FIG. 56, the stylus 622 can then be positioned and/oradjusted to assess a level of the anterior cortex resection. Forexample, with the knee joint in full flexion, the tip of the stylus 622can be brought down and into contact with the femur. The stylus 622 canthen be moved along the femur to measure or identify a desired size forthe femoral knee joint prosthetic.

In some embodiments, an additional device can be used to project a laserbeam or beams onto the resected distal surface of the femur to create across pattern. This cross pattern can be used, for example, to check therotational orientation of the knee distraction device 612 relative tothe femur by comparison of the positions of the beams relative to theepicondylar axis of the femur and a Whiteside's line.

As shown in FIG. 56, once the knee distraction device 612 is alignedwith the mechanical axis, holes can be drilled into the femur, andreference pins 647 can be inserted. The reference pins 647 can beinserted into various openings 646, again depending on the desired angleof resection. For example, and as described above, some of the openings646 can be located at slightly different levels or elevations on theinner body portion 616. Depending on where the reference pins 647 areinserted, a slightly different angle of resection can be achieved (e.g.zero degrees, plus three degrees, minus three degrees relative to aplane perpendicular to the mechanical axis in the tibia).

Once the reference pins 647 are inserted, a cutting block 650 can beplaced onto or coupled with the reference pins 647, for example as shownin FIG. 57. A saw or other cutting device can then make appropriate PFCcut or cuts (e.g. an anterior, additional posterior, and/or chamfer)along the femur.

IV. Attachment of Prosthetic Components

Once all of the tibial and/or femoral cuts are made with the systemsand/or methods described above, a knee joint prosthetic or prostheticscan be attached to the distal femur and/or proximal tibia. The kneejoint prosthetic devices can comprise a replacement knee joint. Thereplacement knee joint can be evaluated by the user to verify thatalignment of the prosthetic components in the replacement knee jointdoes not create any undesired wear, interference, and/or damage to thepatient's anatomy, or to the prosthetic components themselves.

V. User Interfaces

The systems and methods described above can each incorporate the use ofa measuring device, such as, for example, the surgical orientationdevice 12. As described above, the surgical orientation device 12 cancomprise at least one user input, a display and an electronic controlunit. The user inputs and display, and/or the combination of the inputs,display, and electronic control unit can together form part of aninteractive user interface. For example, the interactive user interfacecan comprise a housing (e.g., housing 20 described above), a couplingmember (e.g., coupling device 14 described above) formed on or withinthe housing configured to removably couple the user interface to analignment device (e.g., universal jig 16 described above), a sensor(e.g., sensor 40 described above), an electronic control unit (e.g.,electronic control unit 1102 described above), a user input (e.g., userinput 26 described above, which can transmit input commands to theelectronic control unit), and a display (e.g., display 24 describedabove).

The interactive user interface can comprise a graphical user interfacehaving an interactive window displaying on-screen graphics. For example,the interactive user interface can provide the user with a plurality ofscreen displays. The screen displays can illustrate the steps to beperformed in a surgical procedure and can guide the user through theperformance of the steps. Each screen display can comprise one or moreon-screen graphics. The on-screen graphics can comprise one or morevisual cues or indicators to prompt the user as to what step or steps totake next during one of the procedural methods described above. Thevisual cues referenced herein can comprise instructive images, diagrams,pictorial representations, icons, animations, visual cues, charts,numerical readings, measurements, textual instructions, warnings (visualand/or audible), or other data. The interactive user interface can beconfigured to alter attributes (e.g., color) of the on-screen graphicsaccording to one or more data protocols. The interactive user interfacecan provide visual feedback to the user during performance of one ormore surgical procedures. In certain embodiments, the interactive userinterface can be configured to generate graphical user interface (“GUI”)images to be displayed to the user. As described above, the user caninteract with the surgical orientation device 12 via one or more userinput devices 1114 (e.g., buttons, switches, touchscreen displays,scroll wheel, track ball, keyboard, remote controls, a microphone inconjunction with speech recognition software). The interactive userinterface further can allow the user to confirm that a step has beencompleted (for example, by pressing a user input button). Theinteractive user interface can allow the user to enter data (e.g., anumerical value, such as a distance, an angle, and/or the like), verifya position of the surgical orientation device 12, turn a visiblealignment indication system on and off, and/or turn the entire surgicalorientation device on and off. In certain embodiments, the interactiveuser interface provides one or more drop-down lists or menus from whicha user can make selections. For example, the user can make selectionsfrom a drop-down list using a scroll wheel, trackball, and/or a seriesof button presses. In some embodiments, the user interface provides adrop-down list of predicates that dynamically updates based on userinput.

In at least one embodiment, a module for creating an interactive userinterface can comprise a computer readable medium having computerreadable program code embodied therein. The computer readable programcode can comprise a computer readable program code configured to displayone or more of a plurality of GUI images on a user interface of asurgical orientation device, the GUI images comprising instructiveimages related to the performance of a surgical procedure. The computerreadable program code can be configured to receive instructions from auser identifying the surgical procedure to be performed (e.g., whichjoint and/or right or left). The computer readable program code can beconfigured to show the user steps to be performed in the identifiedprocess for the identified surgical procedure. The computer readableprogram code can be configured to guide the user in performance of thesteps. For example, the computer readable program code can be configuredto receive from the user an instruction to continue to the next step inthe procedure, to receive orientation data from a sensor mounted withinthe surgical orientation device, and to display the orientation data onthe user interface of the surgical orientation device.

In at least one embodiment, the surgical orientation device 12 describedabove can comprise a display module configured to display informationand a sensor module configured to monitor the position and orientationof the surgical orientation device 12 in a three-dimensional coordinatereference system, and to generate orientation data corresponding to themonitored position and orientation of the surgical orientation device.The surgical orientation device 12 can further comprise a control moduleconfigured to receive the orientation data from the sensor module andconvert it to objective signals for presentation on the display module,the control module also configured to display a set of GUI images orother on-screen graphics on the display module, the GUI images oron-screen graphics representing the orientation data received from thesensor module and also representing instructive images related to theperformance of the joint replacement surgery.

In at least one embodiment, the surgical orientation device 12 canreceive orientation data from a sensor module, receive input commandsfrom a user input module to store orientation data from a user inputmodule, convert the orientation data to a human readable format forpresentation on a display device, and display on the display deviceon-screen graphics or GUI images for communicating information to a userbased on the input commands and the orientation data, the informationcomprising instructive images for performing a joint replacement surgeryand one or more visual indicators of a current orientation of thedisplay device with respect to a fiducial, or reference, orientation.

In at least one embodiment, the surgical orientation device 12 describedherein can comprise a sensor module attached to an alignment jig andconfigured to measure and record a fiducial orientation and tocontinuously collect orientation data of the surgical orientationdevice, a display module configured to display at least one visualindicator of the orientation of the surgical orientation device withrespect to the fiducial, or reference, orientation, the display modulefurther configured to display instructive images of one or more steps tobe performed by the surgeon during the joint replacement surgery, and acontrol module configured to receive the orientation data and to convertthe orientation data to objective signals for presentation on thedisplay module.

FIG. 58A-61K show various screen shots which can form part of theinteractive user interface or interfaces described above. For example,FIGS. 58A, 58B, and 58C illustrate display screen shots for assisting auser in using a measuring device, for example the surgical orientationdevice 12. The screen shots can be seen, for example, on a display ofthe measuring device when the device is in startup mode, standby mode,and system fault mode (e.g., system failure mode), respectively.

As shown in FIG. 58A, an interface screen can illuminate in response topressing a user input, e.g., a center button on the surgical orientationdevice 12. Thereafter, a message can be displayed indicating to the userthat the surgical orientation device 12 is preparing for operation. Themessage can be a display of text on a screen, as illustrated in FIG.58A, an audible sound, or other signal to the user to wait for thedevice to confirm a proper operational state. For example, a variety ofself-tests can be performed. In one embodiment, information about theoperating system, such as its version, can be displayed for review.

FIG. 58B shows an operational state of the surgical orientation device12 in which the surgical orientation device 12 is ready to receive inputindicating that a procedure can begin. The surgical orientation device12 can be configured to prompt the user to initiate operation whenready, for example by pressing a user input 26. In one embodiment of asurgical orientation device 12, the user input 26 can comprise a buttonprovided on a front face of the surgical orientation device 12. Theimage in FIG. 58B can be displayed in response to pressing a centerbutton of the surgical orientation device 12 while the image on FIG. 58Ais displayed. In other embodiments, the user can press one or morebuttons while the image in FIG. 58A is displayed in order to initiatethe surgical orientation device 12 for use with surgical procedures fordifferent joints (e.g. right knee joint, left knee joint, right hipjoint, left hip joint, either right or left hip joint). For example, theuser can toggle among displays for each joint until the setting for theappropriate joint is found. In the standby mode of FIG. 58B, the display24 can provide an on-screen graphic of one or more parameters to be usedduring the procedure. For example, a numerical display can be providedfor one or more angles, such as flexion-extension angles, varus-valgusangles, or rotation angles (e.g. angles of rotation about the mechanicalaxis of the leg). The on-screen graphic can comprise alphanumeric textor symbols of various colors, one or more background colors, one or moreicons, one or more GUI images, animations, arrows, and the like.

FIG. 58B also illustrates that textual instructions regarding how tobegin a procedure once the type of procedure has been selected. Forexample, a visual cue can be provided on the display 24 to start aprocedure. FIG. 58B shows that the word “START” can be displayed alongwith an arrow pointing toward a button or other device.

FIG. 58C illustrates a visual notification or warning screen. In certainembodiments, the color of the background of the display can be changedwhen the device is operating in the fault mode. The interactive userinterface can also provide an audible alarm or other audible indicationto the user when the device is in a system fault mode. This displayscreen can be configured such that the screen is displayed when thesurgical orientation device 12 fails to pass a self test or tests thatcan automatically be initiated by the surgical orientation device 12before or during use of the surgical orientation device 12.

FIG. 59A shows a display screen shot which can instruct the user toposition a surgical instrument, for example, an extramedullary device(e.g. the extramedullary alignment guide 313) and/or a cutting block, onthe tibia. In one embodiment, the display screen shot can include animage of the tibia and the surgical instrument displayed adjacent to aparticular aspect of the tibia (e.g., the anterior surface). Theinstructive images in FIG. 59A can be displayed in response to pressinga button located immediately below the arrow displayed in FIG. 58B. In apreferred arrangement, the user can move from one screen to thefollowing screen by pressing a button indicated below an arrow displayedon the current screen, and can navigate back to prior screens bypressing a different button on the surgical orientation device 12 (forexample a left arrow or BACK button). In certain embodiments, a user canpower off the display screen by pressing two different buttonssimultaneously.

FIG. 59B shows a display screen shot which can instruct the user toprovide an orientation assembly (e.g. tibial preparation system 310 a).In one method, the user can be provided with an image of the surgicalorientation device 12 or other measuring device and the landmarkacquisition assembly 312, and the visual cues of FIG. 59B can instructthe user to couple these structures together. The visual cues caninclude an animation or series of animations. The screen shotillustrated in FIG. 59B, as well as other screen shots described herein,can illustrate that the user interface can include a combination ofvisual cues or indicators to provide instructions to the user. Forexample, text can be provided along with instructive images or icons. Insome embodiments, either text or visual cues can be provided alone. Inanother embodiment, audible cues can be provided alone or in combinationwith text and/or visual cues. The audible cues can comprise, forexample, speech, a buzzer, or an alarm.

FIG. 59C shows a display screen shot which can instruct the user toposition an orientation assembly (e.g. tibial preparation system 310 a)in a coronal plane of the tibia and to direct the surgical orientationdevice 12 or other measuring device to acquire the coronal plane of thetibia. The instructive images in FIG. 59C can be displayed in responseto pressing the central button located immediately below the arrowdisplayed in FIG. 59B.

In one method, such as one of the methods described above, the user canbe provided with a surgical orientation device 12 or other measuringdevice and a landmark acquisition assembly 312, coupled together. Thevisual cues of FIG. 59C can instruct the user to position the tibialpreparation system 310 a with respect to the tibia by palpating andplacing a tip 326 of a secondary rod 320 of the landmark acquisitionassembly 312 on the location of attachment of the lateral collateralligament to the proximal fibular head, and placing a second tip 326 onthe apex of the lateral malleolus.

FIG. 59C can further instruct the user to press a button of the surgicalorientation device 12 indicated by the screen (for example by a greenarrow) to direct the surgical orientation device 12 to acquire thecoronal plane of the tibia. In one embodiment, the user interface canprovide information on the status of the process of acquiring thecoronal plane, as well as instruction for operation of the surgicalorientation device 12. For example, the bottom right hand corner of thedisplay 24 can provide information on the status of the acquisition ofthe coronal plane. The information on the screen regarding the status ofthe acquisition of the coronal plane can be designed to attract theattention of the user by, for example, flashing a first color such asgreen to indicate that the surgical orientation device 12 is aligned anda second color, such as grey, to indicate that the surgical orientationdevice 12 is out of alignment.

This color indication can be combined with a more specific visual cuesuch as the visual depiction of the degree of alignment of the surgicalorientation device. After the user has pressed a button on the surgicalorientation device directing the surgical orientation device 12 toacquire the coronal plane, the surgical orientation device 12 caninitiate a recording of the output of one or more sensors. Suchrecording can follow the application of a data protocol that is selectedto minimize error in the measurement, e.g., excluding transient readingand processing readings over a period, such as by employing median andaveraging techniques or stabilization algorithms as described above orotherwise manipulating the readings. In certain embodiments, the dataprotocol is selected to record in memory the last stable datameasurement received before the button was pressed.

In addition, in certain embodiments, the screen in FIG. 59C can providethe user with feedback as to whether the surgical orientation device 12is being maintained parallel (e.g. within an allowable range) to thecoronal plane of the tibia. For example, the display 24 can provide theuser with feedback on the rotation (e.g. roll) of the surgicalorientation device 12 about a first axis. Instead of displaying a degreemeasurement, the display 24 can be configured to display a pictorialrepresentation of a bubble that, for so long as the surgical orientationdevice 12 remains parallel to the coronal plane of the tibia within anallowable range, stays within the confines of two vertical lines, oneline on either side of the bubble. The two vertical lines marking theconfines of the “level” orientation range can correspond to a relativeangle or tilt of plus and minus three degrees or plus and minus onedegree, for example. If the bubble moves beyond either of these lines,the background color of the display 24 behind the bubble can change, forexample, from green to amber, to indicate that the orientation is out ofthe acceptable range.

FIG. 59C also shows that a visual cue which can be provided to the userthat the surgical orientation device 12 is in the process of acquiringthe coronal plane. For example, the text “ACQUIRING” can appear on thedisplay 24. The text “ACQUIRING” can instruct the user to continue tomaintain the orientation of the surgical orientation device 12 so thatthe surgical orientation device 12 is aligned with the coronal plane.

FIG. 59D shows a display screen shot which can instruct the user toreposition or move the surgical orientation device 12, or othermeasuring device, such that the surgical orientation device 12 isattached to a surgical instrument (e.g. extramedullary alignment guide313) on the tibia. The on-screen graphic of images and visual cues ofFIG. 59D can be displayed in response to pressing the central buttonlocated immediately below the arrow displayed in FIG. 59C.

In one embodiment, the screen shot in FIG. 59D can comprise a visual cueor indicator which can comprise an image of the tibia and the surgicalinstrument displayed adjacent to a particular aspect of the tibia (e.g.,the anterior surface), with the surgical orientation device 12 or othermeasuring device coupled with an anterior surface or side of thesurgical instrument.

FIG. 59D can also show a visual cue which can instruct the user tomaintain the tibia in its current position while carrying out the otherinstructions of FIG. 59D. Maintaining the tibial position at this stageof the procedure can be one way of minimizing error in the use of dataacquired by the surgical orientation device 12. In certain embodimentsof the surgical orientation device 12, the screen in FIG. 59D canprovide feedback as to whether the surgical orientation device 12 isbeing maintained parallel (e.g. within an allowable range) to thecoronal plane of the tibia, for example by employing the same bubblepictorial method, or GUI image, described for FIG. 59D above. Suchfeedback can inform the user of any unacceptable rotation (e.g. roll) ofthe surgical orientation device 12.

FIG. 59E shows a display screen shot which can inform the user to setthe posterior slope of a cutting block (e.g. cutting block 84) or othersurgical instrument operatively coupled to the anterior side of thetibia. The instructive images in FIG. 59E can be displayed in responseto pressing the central button located immediately below the arrowdisplayed in FIG. 59D.

For example, the bottom left hand corner of the screen shown in FIG. 59E can provide a degree measurement of the posterior slope being set bythe user in real time as the surgical instrument (e.g. extramedullaryalignment guide 313) and surgical orientation device 12 are adjusted,and can inform the user to insert a first pin through the cutting blockand into the proximal tibia. In certain embodiments, the screen in FIG.59E can provide feedback as to whether the surgical orientation device12 is being maintained parallel (e.g. within an allowable range) to thecoronal plane of the tibia, for example by employing the same bubblepictorial method described for FIG. 59C. Such feedback can enable theuser to control variation in the rotation (e.g. roll) of the surgicalorientation device 12 within an acceptable limit. FIG. 59E shows ananimated depiction of the pin being inserted through the cutting blockand into the proximal tibia, to suggest its insertion by the user. Atext instruction and/or audible signal can be provided instead of, or inaddition to, the animated depiction. For example, a text instruction canbe combined with an animated depiction to provide a more comprehensivevisual cue.

FIG. 59F shows a display screen shot which can instruct the user tocommand the surgical orientation device 12 to acquire a sagittal planeof the tibia. As described above, the sagittal plane can be a planeextending through anterior and posterior surfaces of the tibia andincluding the portion of the mechanical axis extending through thetibia. The images in FIG. 59F can be displayed in response to pressingthe central button displayed in FIG. 59E.

The display screen shot shown in FIG. 59F can also instruct the user tomaintain the tibia in its current position as a way of minimizing errorsthat might result from movement of the tibia. Such a visual cue caninclude, for example, a text instruction located at the top of thescreen and an arrow directed at a button. Pressing a button can activatea light source on the device (e.g. laser 42), which can be directeddistally. For example, the surgical orientation device 12 can includethree user inputs 26 in the form of buttons extending from left to rightacross the surgical orientation device 12, and the arrow can direct theuser to press the button furthest to the right.

FIG. 59G shows a display screen shot which can instruct the user to setthe varus/valgus angle of the cutting block (e.g. cutting block 84) orother surgical device. The images in FIG. 59G can be displayed inresponse to pressing the central button displayed in FIG. 59F.

The bottom right hand corner of the screen shown in FIG. 59G can providea real-time degree measurement of the varus/valgus angle of the surgicalorientation device 12 and the cutting block. This degree measurement cancorrespond to the varus/valgus angle of a cutting plane. The pictorialrepresentation of the proximal tibia and cutting block at the right ofthe screen can informs the user to insert a second pin through the blockand into the proximal tibia. FIG. 59G can also provide an animateddepiction of the second pin being inserted through the block and intothe proximal tibia, to suggest its insertion. The left-hand portion ofthe screen can show the varus/valgus angle of the surgical orientationdevice 12 and the cutting block graphically.

FIG. 59H shows a display screen shot illustrating a degree measurementof the angles of proximal tibia resection, based on the angle of thesurgical orientation device 12 and the cutting block with respect to thetibia. In one embodiment, the screen can provide both theanterior-posterior angle and the varus/valgus angle of the cutting blockboth in degree measurement and pictorially. The images in FIG. 59H canbe displayed in response to pressing the central button displayed inFIG. 59G.

FIGS. 60A, 60B, 60C, and 60D show display screen shots that can bedisplayed by the interactive user interface of the surgical orientationdevice 12 or other measuring device in connection with preparation of aportion of a joint. For example, the screen shots shown in FIGS. 60A,60B, 60C, and 60D can be displayed in connection with a femoral cutand/or knee distraction as described above. In at least one kneeprocedure, various steps can be performed by the user prior to the userinterface interactions illustrated in FIGS. 60A, 60B, 60C, and 60D. Forexample, a tibial resection can be performed using one of the systemsand/or methods described above. After these procedures are complete, theuser can use and refer to the display screens of FIGS. 60A, 60B, 60C,and 60D.

FIG. 60A shows a display screen shot which can inform the user that thesurgical orientation device 12 is in a “Femoral Preparation” mode, andcan provide an image of an arrow instructing the user to push a button(e.g., a center button on the surgical orientation device 12) when theuser is ready to continue the procedure. The images in FIG. 60A can bedisplayed, for example, in response to pressing the central buttondisplayed in FIG. 59H.

FIG. 60B shows a display screen shot which can, for example, inform theuser that the surgical orientation device 12 is in an“Extension-Balancing” mode. The images in FIG. 60B can be displayed inresponse to pressing the central button displayed in FIG. 60A.

The display screen shot shown in FIG. 60B can provide a visual cueinforming the user that the knee being operated on can be in anextension position and that a knee distraction device (e.g. kneedistraction device 612), coupled with the surgical orientation device12, can be inserted into the knee joint and into contact with the femur.

FIG. 60B can further illustrate a visual cue instructing the user toadjust the knee distraction device to balance the tension between theligaments in the knee. For example, the screen shot shown in FIG. 60Bcan contain a visual cue directing the user to align a tibial laser,which can shine distally from the surgical orientation device 12 alongthe direction of the tibia, and a femoral laser, which can shineproximally from the surgical orientation device 12 along the directionof the femur, with certain landmarks on the body. The display screenshot shown in FIG. 60B can also display information indicating that auser input 26 (e.g. button) can be pushed on the surgical orientationdevice 12 to turn the laser off.

FIG. 60C shows a display screen shot which can, for example, inform theuser that the surgical orientation device 12 is in a “Flexion-Balancing”mode. The images in FIG. 60C can be displayed in response to pressingthe central button displayed in FIG. 60B.

The display screen shot shown in FIG. 60C can provide a visual cueinforming the user that the knee being operated on can be in a flexionposition and that a knee distraction device (e.g. knee distractiondevice 612), coupled with the surgical orientation device 12, can beinserted into the knee joint and into contact with one or more femoralcondyles. The display screen shot shown in FIG. 60C can furtherillustrate a visual cue instructing the user to adjust the kneedistraction device to balance the tension between the ligaments in theknee. For example, the surgical orientation device 12 can contain avisual cue directing the user to align a tibial laser, which can shinedistally from the measuring device along the direction of the tibia,with one or more landmarks on the body. The display screen shot shown inFIG. 60C can also display information indicating that a user input 26(e.g. button) can be pushed on the surgical orientation device 12 toturn the laser off.

FIG. 60D shows a display screen shot which can, for example, inform theuser that the surgical orientation device 12 is in a “Femoral-Sizing”mode, and can illustrate a flexed knee being sized. The sizing can beaccomplished in any suitable manner, such as by using a stylus. Thedisplay screen shot shown in FIG. 60D can also display informationindicating that a user input 26 (e.g. button) can be pushed on thesurgical orientation device 12 to turn the laser off. The images shownin FIG. 60D can be displayed in response to pressing the central buttonin FIG. 60B.

FIGS. 61A-K show display screen shots that can be displayed by the userinterface of the surgical orientation device 12 or other measuringdevice in connection with preparation of a portion of a joint. Forexample, the screen shots shown in FIGS. 61A-K can be displayed inconnection with a tibial preparation described above.

FIG. 61A shows a display screen shot which can, for example, inform theuser that the surgical orientation device is in a joint selection mode.The user can select which knee (right or left) will be operated on bypressing a user input 26 on the surgical orientation device 12. Forexample, the user can press a left button for the left knee, and a rightbutton for the right knee.

FIG. 61B shows a display screen shot which can provide a visual cueinforming the user that an orthopedic fixture (e.g. universal jig 16)can be assembled, if it has not already been assembled. The images inFIG. 61B can be displayed in response to pressing a button locatedimmediately below the arrow or arrows displayed in FIG. 61A.

FIG. 61C shows a display screen shot which can provide a visual cueinforming the user that the universal jig 16 can be coupled to thesurgical orientation device 12, for example with the coupling device 14described above. The images in FIG. 61C can be displayed in response topressing a button located immediately below the arrow displayed in FIG.61B.

FIG. 61D shows a display screen shot which can provide a visual cueinforming the user that a tibia preparation system (e.g. tibiapreparation system 10) can be positioned adjacent an anterior surface ofthe tibia. For example, the screen in FIG. 61D can provide a visual cueinforming the user that the tibial preparation system 10 can bepositioned and/or moved until the surgical orientation device 12 isgenerally centered with the insertion of an anterior cruciate ligamentand a medial tibial insertion of the patella tendon in a patient's knee.

The images in FIG. 61D can be displayed in response to pressing a buttonlocated immediately below the arrow displayed in FIG. 61C. In apreferred arrangement, the user can move from one screen to thefollowing screen by pressing a button indicated below an arrow displayedon the current screen, and can navigate back to prior screens bypressing a different button on the surgical orientation device 12 (forexample a left arrow or BACK button).

In some embodiments, the screen in FIG. 61D, or other screens, canprovide the user with feedback as to whether the surgical orientationdevice 12 is being maintained parallel (e.g. within an allowable range)of an anatomical plane. For example, in one embodiment, the userinterface can provide information on the status of the process ofacquiring the coronal and/or sagittal planes containing the mechanicalaxis, as well as instructive images or textual instructions regardingoperation of the surgical orientation device 12 or steps to be performedin a surgical procedure.

In some embodiments, the interactive user interface can be configured todisplay a red “shaky hand” on-screen graphic or icon to indicate to theuser that the device is not currently receiving stable measurements. Incertain embodiments, the electronic control unit 1102 can be configuredto ignore user attempts to register or record reference angles when the“shaky hand” icon is being displayed. The display 24 can also provide atextual, audible, or other visual notification to the user that thecurrent measurements are unstable. As one example, the background colorof the display screen or the color of the measurement readings can bechanged when the current measurements are unstable.

As described above, the display 24 can display an on-screen graphic of abubble (as described above) that, for so long as the surgicalorientation device 12 remains parallel to the coronal and/or sagittalplane of the tibia within an allowable range, stays within the confinesof two vertical lines, one line on either side of the bubble. If thebubble moves beyond either of these lines the background color of thedisplay 24 behind the bubble can change, for example, from green toamber, to indicate that the orientation is out of the acceptable range.

FIG. 61E shows a display screen shot which can provide a visual cueinforming the user that a centering stylus, or other measuring device(e.g. measuring device 109 a), can be used to measure a first distancefrom an A/P point on top of the tibia to an optical element 32 on thesurgical orientation device 12. The images in FIG. 61E can be displayedin response to pressing a button located immediately below the arrowdisplayed in FIG. 61D.

FIG. 61F shows a display screen shot which can provide a visual cueinforming the user that a target probe (e.g. target probe 18 a) can beadjusted such that its length corresponds to the distance measured bythe measuring device. The images in FIG. 61F can be displayed inresponse to pressing a button located immediately below the arrowdisplayed in FIG. 61E.

FIG. 61G shows a display screen shot which can provide a visual cueinforming the user that the lateral malleolus can be palpated, and thata target probe (e.g target probe 18 a) can be held or affixed adjacentthe lateral malleolus. The screen in FIG. 61G can also provide a visualcue informing the user that a cross-hair laser can be directed towardsthe probe 18 a, and the user can press a user input 26 to register thelateral malleolus. The images in FIG. 61G can be displayed in responseto pressing a button located immediately below the arrow displayed inFIG. 61F.

FIG. 61H shows a display screen shot which can provide a visual cueinforming the user that the medial malleolus can be palpated, and that atarget probe (e.g. target probe 18 b) can be held or affixed adjacentthe medial malleolus. The screen in FIG. 61G can also provide a visualcue informing the user that a cross-hair laser can be directed towardsthe probe 18 a, and the user can press a user input 26 to register thelateral malleolus. The images in FIG. 61H can be displayed in responseto pressing a button located immediately below the arrow displayed inFIG. 61G.

FIG. 61I shows a display screen shot which can provide a visual cueinforming the user that a universal jig (e.g. universal jig 16) can beadjusted to adjust the resection plane along the proximal tibia. In oneembodiment, the screen can provide both an anterior-posterior angle anda varus/valgus angle of the cutting block 84 both in degree measurementand pictorially. The images in FIG. 61I can be displayed in response topressing a button located immediately below the arrow displayed in FIG.61H.

FIG. 61J shows a display screen shot which can provide a visual cueinforming the user that the resection depth for the tibial cut can beset. For example, the screen can continue to provide both ananterior/posterior angle and a varus/valgus angle of the cutting block84 in degree measurement and pictorially. The images of FIG. 61J can bedisplayed in response to pressing a button located immediately below thearrow displayed in FIG. 61I.

FIG. 61K shows a display screen shot which can provide a visual cueinforming the user a tibial preparation procedure has completed. Thescreen can include a visual indication that once the procedure has beencompleted for one joint (e.g. left knee), the user can proceed toanother joint. For example, the screen can include an arrow pointing toa user input 26. The user can press the user input 26 to proceed to thenext joint. In other embodiments, the display 24 of the interactive userinterface can be configured to automatically shut off after theprocedure is completed.

Although these inventions have been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present inventions extend beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the inventions and obvious modifications and equivalentsthereof. In addition, while several variations of the inventions havebeen shown and described in detail, other modifications, which arewithin the scope of these inventions, will be readily apparent to thoseof skill in the art based upon this disclosure. It is also contemplatedthat various combinations or sub-combinations of the specific featuresand aspects of the embodiments can be made and still fall within thescope of the inventions. It should be understood that various featuresand aspects of the disclosed embodiments can be combined with orsubstituted for one another in order to form varying modes of thedisclosed inventions. Thus, it is intended that the scope of at leastsome of the present inventions herein disclosed should not be limited bythe particular disclosed embodiments described above.

1. A surgical orientation device, for use in a total knee arthroplastyprocedure, the surgical orientation device having an associatedthree-dimensional coordinate reference system, the device comprising: aportable housing configured to connect to a knee bone by way of one ormore orthopedic fixtures; a sensor located within the housing, thesensor configured to monitor the orientation of the housing in thethree-dimensional coordinate reference system, the sensor furtherconfigured to generate orientation data corresponding to the monitoredorientation of the surgical orientation device, wherein the sensorcomprises a multi-axis accelerometer; a display module configured todisplay one or more angle measurements corresponding to an offset from aflexion-extension angle or a varus-valgus angle of a mechanical axis ofthe knee joint; wherein the sensor is oriented relative to the housingat an acute angle to maximize the sensitivity of the sensor when coupledto a tibia or a femur.
 2. The surgical orientation device of claim 1,further comprising a control module configured to convert a signal fromthe sensor into an angle output to be displayed by the display module.3. The surgical orientation device of claim 2, wherein the angle outputis relative to a reference plane or angle stored in the surgicalorientation device.
 4. The surgical orientation device of claim 1,wherein the multi-axis accelerometer comprises a dual axisaccelerometer.
 5. The surgical orientation device of claim 1, furthercomprising a visual alignment system configured to direct an opticalprobe from a proximal or distal portion of the surgical orientationdevice to illuminate one or more anatomical landmarks.
 6. The surgicalorientation device of claim 5, wherein the visual alignment systemcomprises a laser.
 7. The surgical orientation device of claim 1,further comprising a first laser mounted in the housing to direct lightproximally from the housing and a second laser mounted in the housing todirect light distally from the housing.
 8. The surgical orientationdevice of claim 1, wherein the sensor is adapted to provide position andorientation information relative to the reference system.
 9. Thesurgical orientation device of claim 8, wherein the sensor comprisesgyroscopic sensors to detect angular position changes and accelerometersto detect linear position changes.
 10. An orthopedic orientation system,for use in a joint procedure, comprising: an orthopedic fixture adaptedto be coupled with a knee bone and to be adjustable in multiple degreesof freedom; a surgical orientation device having an associatedthree-dimensional coordinate reference system, the device comprising aportable housing configured to connect to a knee bone by way of theorthopedic fixtures; a sensor located within the housing, the sensorconfigured to monitor the orientation of the housing in thethree-dimensional coordinate reference system, the sensor furtherconfigured to generate orientation data corresponding to the monitoredorientation of the surgical orientation device; an output deviceconfigured to inform a user of the orientation of the device relative toa reference plane corresponding to a mechanical axis of the joint;wherein the sensor is configured for optimum sensitivity in the range ofmotion of the orthopedic fixture.
 11. The system of claim 10, whereinthe sensor is a dual axis accelerometer and is oriented within thehousing such that when the surgical orientation device is coupled to aknee in flexion with a longitudinal plane of the housing parallel to acoronal plane of the tibia, the sensor is at an acute angle relative tothe direction of gravity.
 12. The system of claim 10, wherein the sensoris a dual axis accelerometer and is oriented within the housing suchthat when the surgical orientation device is coupled to a knee inextension with a longitudinal plane of the housing parallel to a coronalplane of the knee, the sensor is at an acute angle relative to thedirection of gravity.
 13. The system of claim 12, wherein the sensor isa dual axis accelerometer and is oriented within the housing such thatwhen the surgical orientation device is coupled to a knee in flexionwith a longitudinal plane of the housing parallel to a coronal plane ofthe knee, the sensor is at an acute angle relative to the direction ofgravity.
 14. The system of claim 10, wherein the sensor is a three axisaccelerometer and further comprises a control module configured toconvert a first plurality of sensor outputs into an angle output to bedisplayed by the display module when the surgical orientation device isin a first range of positions relative to gravity and further isconfigured to convert a second plurality of sensor outputs into an angleoutput to be displayed by the display module when the surgicalorientation device is in a second range of positions relative togravity.
 15. The system of claim 10, wherein the sensor is adapted toprovide position and orientation information relative to the referencesystem.
 16. The system of claim 10, wherein the sensor comprisesgyroscopic sensors to detect angular position changes and accelerometersto detect linear position changes.
 17. The system of claim 10, whereinthe sensor is configured to sense magnetic fields and the surgicalorientation device is configured to determine a change in orientationbased upon such magnetic fields.
 18. The system of claim 17, wherein thesensor comprises a magnetometer.
 19. The system of claim 10, wherein thesurgical orientation device further comprises a first laser mounted inthe housing to direct light proximally from the housing and a secondlaser mounted in the housing to direct light distally from the housing,the orthopedic fixture configured to cause the light to sweep through anangle to illuminate anatomical landmarks in use.
 20. The system of claim10, wherein the surgical orientation device comprises a laser and, thesystem further comprising a device for directing an output of the lasertoward a bone surface.